Construction With Respect To Airtightness Construction Essay

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During Irelands economic growth, new buildings were constructed with little regard to fuel and energy conservation. Buildings where constructed to the minimum standards as set out in the Technical Guidance Documents (TGDs) Part L. With self certified compliance over the last two decades and limited building control officers within local authorities to oversee compliance of these, a great deal of buildings barely meet the minimum requirement. Thermal imaging photos can show these buildings to perform insufficiently in insulation and air-tightness continuity. Many schools built in Ireland during 1990 and 2007 where built with little regard to the conservation of fuels. With the price of natural fuels becoming higher with every passing year, passive standard is becoming a more viable method of construction compared to the traditional cavity wall.

The Kyoto Protocol came into force in 2005 and the proposed targets of reducing Carbon dioxide (CO2) emissions by 8% compared to 1990 levels by the period 2008-2012 became legally binding for EU Member States (UNFCCC, 1997). Ireland's target under the Kyoto Protocol to limit greenhouse gas emissions to 13% above 1990 levels by that period was reached in 1997, and it is likely that the target will be overshot by up to 37% (74Mt CO2) by 2010

In Ireland the residential sector accounts for 26% of primary energy consumption and 27% of energy related CO2 emissions (11,376 kt CO2), the second largest sector after transport at 32%. The average dwelling emits approximately 8.2 tonnes of CO2 emissions, 5 tonnes from direct fuel use and 3.2 tonnes from electricity use (O'Leary et al, 2006) and Irish buildings have a higher consumption of energy, electricity and energy related CO2 emissions per dwelling compared to the average of the European union-15

There are many benefits to having an air tight building. It provides increased comfort levels for occupants, while also having a positive impact on energy use and quality of the indoor environment. Elimination of these can save hundreds on fuel costs every year, along with reducing heat losses.

(O'Leary et al, 2006). (EC, 2005).

Acknowledgements

The author of this dissertation would sincerely like to thank the following people for their support and understanding:

Table of contents.

References 1

Bibliography 2

Appendices 3

List of figures 4

Abbreviations 5

Declaration of Plagiarism 7

Chapter 1 Introduction to dissertation.

Introduction to chapter. 8

Hypothesis

Aims and objectives.

1.4 Parameters and limitations of study.

1.5 Outline of research methods.

1.6 Summary of Chapter 1

Chapter 2 Passive house requirements and standards.

2.1 Introduction to chapter.

2.2 What is Passive Standard?

2.3 Where Passive Standard construction all began.

2.4 European and Irish, objectives and policies.

2.5 Passive standard elements and technologies.

2.2.1 Super Insulation.

2.2.2 Thermal conductivity and heat transmittance.

2.2.3 Passive standard windows and doors.

2.2.4 Thermal bridging.

2.2.5 Passive solar gain.

2.2.6 Space heating and highly efficient ventilation systems.

2.6 Summary of chapter 2

Chapter 3 The effects of Air-tightness on building design.

3.1 Introduction to chapter.

3.2 What is air tightness?

3.3 Air infiltration within the building envelope.

3.3.1 Methods of measurement for air infiltration.

3.4 The associated benefits of minimising air infiltration.

3.5 Summary of chapter 3

Chapter 4 Maree N.S case study, designing for Air-tightness continuity.

4.1 Introduction to chapter.

4.2 considerations to be taken at design stage.

4.2.1 Action to be taken.

4.2.2 Entrance lobby considerations.

4.2.3 Choosing appropriate materials.

4.2.4 Designing for access to air-tight layers.

4.2.5 Inspection of air tight layers.

4.3 Air tightness details and specifications for Maree N.S.

4.4 Testing for air tightness in Maree N.S.

4.5 Summary of chapter 4

Chapter 5 Conclusions

References

Bibliography

Appendices

List of figures

Abbreviations

BRE Building Regulation Establishment.

SEI Sustainable Energy Ireland.

PHI Passive House Institute.

BIM Building Information Modeling.

TGDs Technical Guidance Documents.

N.S National School.

CO2 Carbon Dioxide.

PHPP Passive House Planning Package.

CEPHEUS Cost Efficient Passive Houses as European Standards.

EU European Union.

DCENR. Department of Communications, Energy and National Resources.

PEP Promotion of European Passive House.

EPED European Performance Building Directive.

IEE Intelligent Energy for Europe scheme.

MVHR Mechanical Ventilation Heat Recovery system.

BMS Building Management Systems.

EPS

Low-E Low Emissions.

KWh/M2

KWh/M2A

W/M2k

 < 0.01 W/(MK)

M3/h

Declaration of Plagiarism

Galway Mayo Institute of Technology

BSc (Honours) Architectural Technology

Name: Darren Heneghan

Dissertation title: The application of Passive Standards in school construction with regard to airtightness.

Plagiarism consists of a person presenting another person's ideas, findings or work as ones own by copying reproducing the work without due acknowledgement of the source. Plagiarism is the theft of intellectual property. The institute regards plagiarism is a very serious offence. At the very least it is a misuse of academic conventions or the result of poor referencing practices. Where it is deliberate and systematic plagiarism is cheating.

Plagiarism can take several forms, examples of which are given below;

a Presenting substantial extracts from books, journals, articles, thesis and other published or unpublished work (eg: working papers, seminars and conference papers, internal reports, computer software, lecture notes or tapes and other students work without clearly indicating the source of the material.

b Quoting directly from a source and failing to insert quotation marks around the quoted passages. In such cases it is not adequate merely to acknowledge the source.

c Using very close paraphrasing of sentences or whole paragraphs without due acknowledgement in the form of reference to the original work.

d Copying essays or essay extracts or buying existing essays from internet websites or sources.

e Closely replicating the structure of some ones argument without clear referencing.

The institute is committed to detecting all cases of student plagirisum. All cases will be dealt with in accordance with the institute examinations regulations.

a Awarding lower marks or no marks for the dissertation.

b Awarding a lower class of degree or other academic award.

c Excluding the student from the award of a degree or other academic award which may be either permanent or for a stated period.

PLAGIARISM DECLARATION

By signing this declaration, you are confirming in writing that the work you are submitting is original and does not contain any plagiarized material.

Your Signature: Date:

Chapter 1 Introduction to dissertation.

1.1 Introduction to chapter.

This dissertation researches and demonstrates the application of air-tightness, an element of Passive Standard construction on a National school extension at Maree N.S, Oranmore, Co. Galway. It will explain the benefits associated with utilising an air tight building envelope. This chapter will give the reasons for choosing this topic, the aims, and objectives to be achieved and the methods used to compile this information. Air tightness is one of the key concepts of passive construction, Often the most noticeable impact of poor air tightness is draught and noise. Large amounts of heat are lost with escaping air via windows doors and vents. Any type of building construction can be designed to passive standard. Air tightness can be incorporated into assemblies at design stage when considering construction mythologies.

1.2 Hypothesis.

This dissertation is an attempt to address how air tightness continuity is achieved and design considerations applied to Maree N.S extension using passive standard construction methodologies.

1.3 Aims and objectives.

The aim of this dissertation is to determine Research will take a hypothetical look at the processes involved on applying air tightness to Maree National School and exploring the difficulties on ensuring air tightness continuity around the building envelope at design stage, construction stage and testing upon competition. It will also compare the basic standards of the Department of education school construction guidelines with Passive Standard construction. All elements of the Maree N.S extension will be taken into account using a Building Information Modelling (BIM) with detailing drawn to differentiate between both forms of construction to show how Air tightness is achieved.

With the rise in fuel costs it is becoming more important to decrease buildings heating demands, because of this there is a rise in passive standard construction with air tightness.

The following objectives have been derived in order to achieve this aim:

To critically appraise the issues that arises from applying air tightness within a school building.

To critically appraise the passive house standards compared to department of education standards.

To demonstrate the methods and procedures of applying air tightness into Maree N.S extension design.

Case study on Maree N.S

1.4 Parameters and limitations of the study.

The parameters and limitations of this dissertation will be in accordance with Department of Education, Sustainable Energy Ireland (SEI), European embedding of passive standards, Building Research Establishment (BRE) and Passivhaus Institute Germany. The extension on Maree N.S was not constructed. This dissertation takes a hypothetical view on successfully applying air tightness to the proposed extension. No detailed studies for testing of air tightness and thermal bridging could be carried out and concluded.

1.5 Outline of research methods.

The research methods used to complete this dissertation are of both secondary and primary research. The secondary research methods where obtained and analysed by means of online databases, journals, articles and books. Primary research undertaken used pier reviewed journals and guidelines written by The Department of Education, Sustainable Energy Ireland (SEI), European embedding of passive standards, Building Research Establishment (BRE) and Passivhaus Institute Germany. All primary research was critically analysed to give a perspective

1.6 Summary of chapter 1

To recapitulate, this chapter has given the hypothesis, aims and objectives to be determined in this dissertation and a brief insight into the importance of air tightness, an element of passive construction. The chapter examined the secondary and primary research methods and the limitations inferred on this research.

Chapter 2 Introduction to Passive house requirements, E.U and Irish guidelines.

2.1 Introduction to chapter.

This chapter will describe the internationally recognised term "Passive Standard" and the establishment of the Passive House Institute by Professors Bo Adamson of Lund University in Sweden and Wolfgang Feist of the Institute for Housing and the Environment in Germany. All associated design elements and technology that are required for Passive Standard construction will be explored with detail with reference to minimum specific measurements scientifically proven by the Passive House Institute, Hassan, Germany.

In addition this chapter will discuss guidelines provided by European Passive House Project CEPHEUS (Cost Effective Passive Houses as European Standards), The Promotion of European Passive House (PEP) and Sustainable Energy Ireland (SEI). The future aims and objectives of these institutes are discussed and

2.2 What is passive house standard?

The term "Passive house standard" refers to an internationally recognised type of building construction that utilises an array of technologies, designs and specialist materials. The standard has been called "passive" because of the heat gains delivered externally by solar irradiation that passes through glazing and heat gains from utilities, occupants and other heat sources maintained internally to fundamentally keep the building at a comfortable 20 degrees indoor temperature all year round. This reduces the space heating requirements to a minimum, if it is required at all. However to achieve this standard extra investment at construction stage are needed but this is offset by the energy savings acquired over a number of years.

""Passive houses" are buildings which assure a comfortable indoor climate in summer and in winter without needing a conventional heat distribution system. To permit this, it is essential that, under climatic conditions prevailing in central Europe, the buildings annual space heating requirement does not exceed 15 kWh/ (M2A)." (CEPHEUS report July 2001)

However the passive standard is not only about energy savings. It is also about high indoor thermal comfort for its occupants. When the indoor air temperatures are at the optimum 20 to 22 degrees, thermal comfort is achieved.

2.3 Where it all began?

The passive house concept was conceived in May 1988 by professors Bo Adamson of Lund University in Sweden and Wolfgang Feist of the Institute for Housing and the Environment in Germany. Their research was realised in Darmstadt-Kranichein, Germany in 1991 with a house constructed as a means of researching the Passive Standard of the building which established the passive construction standards. In Hassan, Germany a scientific research group was formed, financed by the Hessian ministry for economics and technology to promote and control the standards.

From 1988 to 2011 30,000+ Passive House Standard buildings have been constructed. The Passive House Institute (PHI) was established in 1996 as an independent research institute under the leadership of DR. Wolfgang Heist. The institute's objectives advance the research and development of the passive standard concepts. So far it has set the basic building conditions to be meet to acquire passive standard and developed software the Passive House Planning Package (PHPP) to assess before construction that these conditions are meet.

(Sustainable Energy Ireland SEI 2002, PassivHaus Institute)

2.4 European and Irish objectives and policies.

To introduce Passive House concept for a wide market, the European Passive House Project CEPHEUS (Cost Effective Passive Houses as European Standards) was founded. The (CEPHEUS) project was funded by the EU-commission within the framework of the Thermie-Programme BU/00127/97/DE/SE/AT. 221 housing units where built in several European countries and all where closely monitored under (CEPHEUS); taking into account occupancy behavior, with regard to learning knowledge of building technologies and behavior under real interior conditions. The project ran for three years between 1998 and 2001.

The Passive House Institute scientifically led the (CEPHEUS) project. All of the units followed the Passive House Standard. The U Values of the exterior elements ranged from 0.1 W/M2K to 0.15 W/M2K and had a maximum airtightness Value of 0.6 air changes an hour at 50. Measured air rates of mechanical ventilation where 0.25 to 0.4 air changes at regular pressure conditions. The results showed that all buildings within the project consumed extremely low levels of energy with a 50% reduction in energy use. This lead to a fundamental set of conditions required for Passive House Standard.

(Passive House Institute).

The Promotion of European Passive House (PEP) was founded in May 2006 and funded by the European commission of energy and transport under the (IEE) program as a means to promote Passive House concept in Europe by the publication of information booklets on Passive Standard construction. This information outlines barriers, incentives, statistics and guidance on Passive House construction relating to each countries particular climate condition.

The aims of the (PEP) project are as follows:

Make a report on the Passive House concept and provide specific solutions in different European regions and climates.

Document the potential energy savings brought about by use of the Passive House concept.

The adoption of the existing Passive House design tool (PHPP) to meet the demand of architects in different regions.

Develop practical information packages CD ROM based, with practical information such as product information, research results, calculation methods and quality assurance activities.

(PEP May 2006).

Preparation for the international certification scheme for Passive House certification was established in relation to the European Performance Building Directive (EPBD). Nine co-operating European countries (The Netherlands, Belgium, Norway, Denmark, Finland, Germany, Austria and Ireland) started a project. The project was financially supported by the EC, within the framework of the Intelligent Energy for Europe scheme (IEE).

Adapted from ------

Table 1: yearly primary space heating energy uses per dwelling, per existing, typical new and passive house build.

Explain graph

At the beginning of 2004 the term "Passive House" was generally unknown in Ireland. The Passive house concept was first introduced to Ireland by the Swedish architect Hans Eek during the solar conference "see the light 2002" organised by the Sustainable Energy Ireland (SEI). The (SEI) is Irelands national energy authority, established under the sustainable energy act 2002 to implement Irish government policies and objectives on energy usage. It is financed by the Irish government National development plan and part by the European Union.

The (SEI) objectives for Passive House concept in Ireland are as follows:

Assisting deployment of superior energy technologies.

Raising awareness and providing, advice and publicity on best practice for Passive design.

Stimulating preparation of necessary standards and codes.

Publishing statistics and projections on sustainable energy and achievement of targets.

Stimulating research, development and demonstration with the aid of publications.

"(SEI) Passive Homes. Guidelines for the design and construction of Passive House dwellings in Ireland".

"(SEI) Retrofitted Passive homes and Guidelines for upgrading existing dwellings in Ireland to Passive House standard."

(SEI Ireland)

The governments white paper "Delivering a Sustainable Energy Future for Ireland" (DCENR, 2007) was the initiation of change to the Irish building regulations. In 2008 the release of the building regulations amendment S.I. NO. 259/2008 for part L conservation of fuel and energy of the (TGDs) led to a 40% energy reduction and related CO2 emissions in new build construction. The Irish government as of last year introduced amendment S.I. NO. 259/2011, released with the hopes of reducing energy consumption by a further 20%. This is in anticipation of the European PEP directive for all new construction to be Passive Standard by 2015.

(ec.europa.eu).

2.5 Passive standard elements and technologies.

Passive standard building construction is very different to standard building construction. No new building materials are used within the construction but the approach to the building design is key to achieving the passive standard concept. Unlike standard building construction passive standard construction uses an array of specific building techniques. To achieve passive standard well insulated doors and windows need to be fitted, with air tightness continuity through-out the building envelope, super insulation, highly efficient space heating and ventilation systems and the elimination of thermal bridging. Also a Passive standard building to achieve maximum passive solar gains has to be an optimum orientation of 30 degrees either side of south to avoid heat losses during the winter months.

The building envelope consists of all the structural elements which separate the indoor environment from the outdoor environment. Careful consideration of the building envelope details at design stage can reduce the need for space heating maintaining the required 15 kWh/ (M2A) per annum. In table 2 a range of U Values are specified to demonstrate the varying requirements that are needed for Passive Standard. Air leakages and Thermal bridges that would compromise the efficiency of a building have to be eliminated by maintaining continuity of insulation and air tight layers throughout the building envelope.

BUILDING

ELEMENT

EUROPEAN GUIDELINES (P.E.P.)

IRISH GUIDELINES

(S.E.I.)

PASSIVE HOUSE INSTITUTE

Insulation walls

U Value < 0.15W/M2K

U Value < 0.10W/M2K

U Value < 0.15W/M2K

Insulation roofs

U Value < 0.15W/M2K

U Value < 0.09W/M2K

U Value < 0.15W/M2K

Insulation floors

U Value < 0.15W/M2K

U Value < 0.10W/M2K

U Value < 0.15W/M2K

Windows/glazing

U Value < 0.8W/M2K

U Value < 0.8W/M2K

U Value < 0.8W/M2K

External doors

U Value < 0.6W/M2K

U Value < 0.6W/M2K

U Value < 0.6W/M2K

Thermal bridges

 < 0.01 W/(Mk)

 < 0.01 W/(Mk)

 < 0.01 W/(Mk)

Ventilation

 > 75%

 > 85%

 > 75%

Max space heating

15 kWh/m2 per annum

15 kWh/m2 per annum

15 kWh/m2 per annum

Airtightness

n50 < 0.6 per hour

n50 < 0.6 per hour

n50 < 0.6 per hour

Table 2: passive standards for Ireland, Europe and the passive house institute.

Brief explanation of graph

2.5.1 Super insulation.

Super thermal insulation is an important factor for the energy optimization of the building envelope and achieving thermal comfort for its occupants. To comply with Passive Standard, the most effective measure of eliminating heat transmittance is to ensure the continuity of insulation around the entire thermal envelope. Thermo graphic imaging is used to illustrate the difference between an efficient and non-efficient insulation levels through the exterior facades. Heat losses transmitted through the building envelope and around opes are highlighted by blue, green, yellow and red as seen in figure 1. In a Passive House some heat is lost through the opes, heat lost through the external façade is extremely low.

Insulation of the building envelope can be divided into four distinct areas: External wall, Roof, Floor and windows/doors. Existing Passive Houses in Ireland have U Value for walls, floors and roofs range from 0.09 to 0.15 W/ (M2K). Common insulation materials are mineral wool and expanded polystyrene (EPS)

(Feist et al, 2005)

2.5.2 Thermal conductivity and heat transmittance.

Thermal conductivity (-value) relates to a material or substance, and is a measure of the rate at which heat passes through a uniform slab of unit thickness of that material or substance, when unit temperature difference is maintained between its faces. It is expressed in units of Watts per meter per degree (W/mK), (Building Regulations Technical Guidance Document Part L, Conservation of Fuel and Energy 2005).

Materials and constructions, heat transfers from high to low temperature. The use of particular Insulation materials for walls, roofs and floors ought to be considered with regard to thermal conductivity to reduce the amount of thermal losses. The transport of heat can occur in three ways, radiation, conduction and convection. Radiation: Is driven by a difference in temperature, heat is transferred from hot to cold. Convection is driven by a difference in pressure. Conduction is when there is a difference in temperature. The heat then transfers through the material from hot to cold. Heat transfer has to be reduced or eliminated in Passive House design, with the aid of good thermal characteristics and air tightness.

2.5.3 Passive Standard windows and doors.

Passive Standard windows and doors can cover a large proportion of the façade of a building and so play a considerable part in determining its energy requirements. When designing its best to avoid north orientated glazing and fit large windows on the south orientated elevation. This is to minimise thermal heat losses through the north side façade, which receives no direct sunlight and maximises solar radiation heat gains on the south façade.

The average U-value for windows (including glazing and window frames) in the region of 0.60 to 0.80 W/(M2K). These U-values far exceed those currently required under the Irish Building Regulations, with the most marked difference pertaining to windows, wall and floor U Values. As stated in table 2, windows and doors with U Values of < 0.8 W/(M2K) can be combined with opaque areas at < 0.15 W/(M2K) this will easily achieve Passive Standard compared to conventional double glazed window and door units which have one rubber seal. Highly efficient (low-E) coated triple glazed, thermally insulated units include significant draught reduction as there are two seals or gaskets and significant sound insulation. The Passive House Institute provides certification for approved door and window manufactures. For approval all parts of the assembly are tested thoroughly and only then awarded certification. Although it is not required to use certified passive house units, choosing approved units that has been tested and certified means the validity of technical data.

2.5.4 Thermal bridging.

Thermal bridging are weak areas in the insulation continuity of building envelope. Typical places for thermal bridging are between the roof and exterior wall, opes in walls for windows/doors, cables, ventilation ducts and penetrations for services. These can account for up to 50% of all heat lost throughout the building envelope. This is usually from poor design details, lack of knowledge and poor construction methods.

In passive house thermal bridges have to be significantly reduced. The reduction should be made to the degree that the losses through thermal bridges become negligible. Thermal bridges produce unwanted losses of heat energy and in extreme cases can cause surface condensation or interstitial condensation in the building structure, which can initiate mould growth and wood rot. The linear thermal transmittance should not exceed  < 0.01 W/(MK). This can easily be achieved by carefully identifying and locating all potential thermal bridges before construction to provide a continuous insulation layer. Close inspection of all details are required on site to ensure high standard construction practices.

2.5.5 Passive solar gain.

Passive solar gain is the collection of the suns radiation through glazing and solar panels heating the building space and is optimized by orientation of the building 15 degrees either side of due south and placing large windows on the south elevation. As the sun passes during the winter months the suns heat penetrates through the glazing heating the space within the building this reduces the need for mechanical heating.

"Very high quality windows facing south will have a positive thermal balance. it will have more heat gain than heat loss throughout the year." (J. Schnieders, PassivHaus Institute)

There are many gains to be had from large amounts of glazing on the south façade. However, there is a point where diminishing returns come from covering the entire southern elevation in glazing as the heat loss is greater than the heat gains annually. There is no optimal ratio of glazing to floor area that can be used as a rule of thumb in deciding what proportion of a given façade should be glazed. The area of glass has to be determined as part of the design verification procedure using the (PHPP) software.

(passive house institute)

2.5.6 Space heating and highly efficient ventilation systems.

The difference in heat supply in a Passive Standard building compared to a conventional building is that the heat is transported throughout the ventilation system, along with the fresh air supply. To meet the passive standard heat recovery mechanical ventilation heat recovery system (MVHR) is installed with a minimum efficiency of 85%. The primary function of the ventilation system is to maintain excellent indoor air quality and to distribute the heat gains throughout the building. The rate of ventilation is determined according to the Passive House Institute guidelines, which recommend a flow rate of 30 M3/h per person. Cross flow heat recovery systems are usually used in Passive Standard Buildings, cross flow system works by transferring heat from warm stale air to the fresh cold air through a series of channels that are closely spaced but separated in the central core. This prevents contamination of fresh air which prevents risk of so called "sick building syndrome". It is most effective because it could theoretically transfer all the heat from one side to the other. This eliminates the need to completely heat fresh air as it enters the building. The air supply cannot exceed 52 degrees as higher temperatures lead to dust carbonisation in the supply air. Dust particles may fume on hot surfaces within the air supply ducts and produce fowl smells.

In our climate, with lower outdoor temperatures and low internal heat loads, ventilation systems alone may not be sufficient. Other means of heating are required; the ventilation system can be used in conjunction with a water exchange pump, pellets boiler, solar collectors or used in combination. The best practice for reducing the final energy demand is by use of a solar thermal system. The solar thermal panel collects heat radiation from the sun which can be connected to the domestic hot water or the supply air in the ventilation system. According to the Passive House Standard; direct use of electric heating should be avoided because it is connect to the primary energy demand.

(SEI 2002)

(Passivhaus Institute 2001).

2.6 Summary of chapter 2

This chapter divines the term Passive Standard and how it has become an internationally recognised type of building construction. Passive standard requires extra investment at construction stage, but this investment is returned by savings on energy and heating costs over a number of years.

Discussed in this chapter is how the Passive standard concept was conceived by Bo Adamson and Dr Wolfgang Heist 23 years ago in 1988. Their research was only realised in 1991 with a successful prototype building, the outcome of which was the establishment of the Passive House Institute (PHI). Technical advancements of Passive house elements over the past 16 years and the rise in price of fossil fuels has led to many countries promoting and establishing their own means of administering Passive Standard solutions for that countries particular climate. In 2002, at a "see the light" conference Passive House concept was first introduced to Ireland by architect Hans Eek. In 2004 the term Passive House was still generally unknown in Ireland until documents where published Ireland and Europe that outlined the objectives, polices and guidelines to passive house construction as set out by Sustainable Energy Ireland (SEI) and the Promotion of European Passive House (PEP).

The importance of the Passive Standard elements and technologies are explained in some detail super insulation, triple glazed window and doors, elimination of thermal bridging, highly efficient space heating and (MVHR) systems, passive solar gain and air tightness continuity. All are equally important to achieve Passive Standard building certification.

Chapter 3 The effects of air-tightness on building design.

3.1 Introduction to chapter.

The following chapter explains the importance of air tightness through-out the building envelope and its effects both positive and negative. Only since the introduction of Passive Standards has the importance of air tightness been made aware to a wider range of people both in the construction industry and at home. Air tightness is a major factor in reduction of a buildings energy usage, the design team and building contractor assigned to the construction of an air tight building need to be competent and made aware of it importance. Air tightness in building design is being made aware in Ireland by the (SEI) "Passive Homes. Guidelines for the design and construction of Passive House dwellings in Ireland".

This chapter also discusses climate conditions ie: wind pressure, temperature differences, air buoyancy and a buildings orientation and there affects on air conditions between the interior and exterior. This chapter will examine how heat loss is connected to an air permeable building structure and how air flows through the building envelope removing valuable heated air. Also, it will explore thermal comfort levels and how drafts and air movement can affect comfort levels buildings occupants.

3.2 What is air-tightness?

Building an airtight or leak-free structure is imperative to achieving the Passive House Standard. If there are gaps and cracks in the building fabric then uncontrolled amounts of cold external air can infiltrate the building. It is driven by internal and external pressure and temperature differences and is highly variable in response to changes in the weather. Achieving a high level of air tightness eliminates cold draughts and associated comfort losses. It also prevents condensation of indoor moist, warm air penetrating the structure, and possible structural damages due to decay, corrosion and frost. Air-tightness is achieved by careful application of membranes and tapes eg: timber frame or steel structure or wet plastering within the building envelope eg: solid block construction. Penetrations of the airtight layer by mechanical and electrical services must be properly sealed using appropriate airtight sealants.

Build tight, ventilate right. (BRE)

The most critical issue regarding testing for airtightness is timing during the building process. It is important that remedial measures can be carried out in order to remedy any leaks or cracks. The test should be carried out before second fix carpentry, for example, when there are no skirting boards or window boards fitted and where the junctions covered by such materials are still accessible and can be sealed. The test should also be carried out after all mechanical and electrical services, which need to penetrate the building envelope, have been installed. Otherwise, installing such services after the test could severely compromise the air-tightness of the building. The associated second fixing could also lead to a rise in the overall construction cost of the building.

(SEI, 2002)

(BRE)

(Air-tightness in commercial and public buildings 2002).

3.3 Air-infiltration within the building envelope.

Air infiltration is the air leakage through cracks and gaps in the building fabric and is the quantity of the leakiness in the building envelope. Air infiltration is often not in a direct line for outside to inside. Air can filter through the external finish into a cavity traveling horizontally and vertically, then passing through gaps in the construction finally exiting around sockets and skirting. Many air infiltration paths can be minimised by correct design strategies and detailing and onsite inspections at critical stages of construction. It is furthermore affected strongly by design decisions and construction quality.

Temperature changes between inside and the exterior of the building envelope lead to infiltration and can rise and fall uncontrollably, which is in reaction to fluctuations of external wind speed and air temperature changes. Excessive air infiltration will lower the average temperature to an uncomfortable level during high wind conditions. According to the Passive House Institute there are many examples where a leaky envelope has given rise to complaints regarding thermal discomfort. Once a building is constructed it can be very expensive and difficult to rectify.

Wind pressure on the building façade causes pressure differences between the inside and outside of the building. The result is that, air enters on the windward elevation called infiltration and exits on the sides and leeward elevations called exfiltration. The naturally occurring effect creates a small negative pressure internally.

Air buoyancy is created when heat produced by people, heating system, equipment and from solar gain, which makes the internal air more buoyant than the external air, a small negative pressure easily moves this buoyant air through gaps and cracks on the leeward elevation.

Where infiltration is minimised, unchanging ventilation and thermal comfort is easily achievable and maintained. In very extreme weather conditions the occupants should have the option of regulating the ventilation openings to minimise discomfort.

3.3.1 Methods of air infiltration measurement.

3.4 The associated benefits of minimising air infiltration.

In an airtight building the energy costs for space heating may be significantly reduced compared to those for a comparable but air permeable building. Air humidity regulator costs can similarly be reduced by avoiding unwanted air penetration. Tests carried out by the (BRE) on an air permeable building showed that the expulsion of warm air can account for as much as 50% of the total air loss through the building envelope. Total space heating costs in an airtight building may be as much as 40% less.

In a Passive school building with 25 pupils and 1 teacher can save 1.5 KW which can easily keep a classroom comfortable for an entire year. This lowers fuel usage considerably, reducing CO2 emissions released into the atmosphere. The building structure needs to be both airtight and well insulated to achieve these significant savings. Sophisticated energy saving heating control systems, building management systems (BMS) and heat recovery systems (MVHR) are economically feasible options for use in air tight building construction. In an air permeable building, air infiltration may reduce or negate any benefits of such systems. Exfiltration of warm air through permeable building fabric will reduce the heat available to heat recovery systems and can reduce their efficiency by over 20%

(BRE)

3.5 Summary of chapter 3.

Chapter 4 Maree national school case study, designing for

Air tightness continuity.

4.1 Introduction to chapter.

In this chapter, the primary research will take a hypothetical look the processes involved on applying air-tightness to Maree National School and exploring the difficulties on ensuring airtightness continuity around the building envelope at design stage, construction stage and testing upon competition. All elements of the Maree N.S Extension Have been taken into account using a BIM model and detailing drawn to show how this was achieved.

4.2 Considerations taken at design stage.

It's during the design process that all critical decisions on the buildings airtightness are made. Simple detailing of the building envelope is key to the success of airtightness. The main considerations taken into account for the new extension are as follows:

The level of airtightness required.

Setting out how airtightness is achieved with specification.

Choosing correct construction materials used for airtight barriers.

Knowing where to seal around the building envelope.

First the level of air tightness for Maree N.S will need to be established using the BRE recommendations for airtightness. As shown in table 2 below:

Type of construction

Air permeability m3/(h.m2) at 50 pa

Air change rate h-1 at 50 pa

Best practice

Standard

Cold stores

0.2

5.0

----------

Factories

2.0

6.0

----------

Hospitals

5.0

9.0

----------

Museums

1.0

1.5

----------

Passive house

----------

1.0

0.5

Schools

3.0

9.0

----------

Table 2: maximum air filtrations for different building types.

4.2.1 Action to be taken by client, Architect and building contractor.

A plan of action will need to be established to ensure good communication between the Client, Architect and Building contractor. Outlining the main concerns early on will eliminate problems later in the construction process. The steps that are taken are as follows:

Building appraisal: Is to establish the appropriate air tightness for the building construction. As seen in table 2 the best air filtration Maree N.S is 3 air changes per hour.

Outline proposals: Decisions on the construction type and location of air tightness layer will be located in plan and section. as seen in fig -------------

Detail proposals: Details of the building construction drawn up and location of air tightness layer hi lighted for easy understanding. As seen in fig-----------

Contractor informed: After tender documents are sent and contractor chosen, building contractor and sub-contractors are informed on methods of airtightness, with their handling methods and responsibilities outlined.

Practical completion: Before the air tight layer is concealed, building inspections are done by the architect by means of visual inspection and blower door testing.

Completion: occupancy comfort and energy consumption documented and adjustments made to ratify any concerns.

4.2.2 Entrance lobby

To comply with the passive standard and BRE, the main entrance at mare N.S is a drought lobby construction. See fig-------- .For the lobby to work correctly, two sets of doors are set at either end at a minimum of 4 meters apart. These are self-closing with an air curtain to reduce heat losses. Revolving doors where not appropriate as these are used in high traffic buildings, considering the school is at its busiest only in the morning and at collection times the human traffic was not adequate.

4.2.3 Choosing appropriate materials.

An assortment of materials can be used as part of the airtightness layer. These materials are to be chosen with respect to effectiveness and how they are substituted in the future will be carefully considered. These components can be broken into three areas:

Sealants

Sealants are one of the most important mechanisms in guaranteeing effective airtightness. Regularly used in exterior components, as bedding materials for glazing and curtain walling. Efficient sealants are resistant to recurring movements at the joint and maintain adhesion to surfaces and be easily exchanged over the life cycle of the building. Manufacturer's instructions for warranty guarantee purposes should be followed. See fig------

Gaskets

Gaskets are mainly found in window / door components and service penetrations (movement joints) and are made from flexible rubber. All applicable components will have appropriate gaskets within Maree national school. See fig------

Mineral wool

Mineral wool with impermeable coating can be used to provide an air tight seal. Sealing the mineral wool in a polyethylene tube will be used around service penetrations throughout Maree national school. See fig---------

Breather Membranes

Their primary role is to protect the structure against rainwater penetrating the outer skin. They are vapour permeable and allow the escape of moister created within the building to evaporate. Check that the breather membrane can also be used for air tightness by referring to the specification. In Maree N.S breather membranes will be used in the roof construction see fig--------- the membrane is situated underneath the insulation and is sealed to the exterior wall structure to ensure the air tight continuity. For the membrane to be effective all membrane will be fixed using corrosion resistant fixings every 600 c/c to ensure the membrane is kept tight. Membranes should link with adjacent air tightness components, particularly around openings. Flexible tapping that is effective for the whole of its life should be used to seal between membrane layers is crucial and should be done by trained operatives.

4.2.4 Designing for access to airtight layers

The air tightness layers have to be checked and maintained over the buildings life span and designers need to consider in the design how this can be easily achieved. Maree N.S will be standing for many years with repair or replacement being very likely. Placement of the air barrier within the wall construction is very important and can be located either inside or outside wall construction and both have their advantages and disadvantages. See fig-------- inside the wall construction the advantages are: The air barrier and vapour control layer can be combined with the condensation risk reduced. The air barrier is kept at a relativity constant temperature and is less susceptible to thermal cycling with it being easier to maintain and repair during construction. Disadvantages are mainly during the construction phase. Air barrier is more susceptible to damage during the installation of services in the wall. The construction of the air barrio must be sealed to the floor slab, windows and around penetrations to maintain continuity. Outside the wall construction have very little advantages. The air layer can be easily continues over the wall and floor junctions and that the air barrier is protected from construction activities. The disadvantages of this type construction are that long term maintenance and repair is difficult. The positioning and water vapour permeability of an outer air barrier must be considered with reference to the walls vapour transmission characteristics to avoid the possibility of creating a vapour trap, which could create mould.

For this reason I've chosen to locate the air tightness barrier within the wall construction, the tendering of a competent building contractor in passive standard construction is vital with inspection of problem areas at regular intervals by the architect.

4.2.5 Inspection of airtight layers

Inspection of the building envelope is the most important part of the construction process. It is an opportunity to guarantee that the construction team has a clear understanding of the importance of protecting the air tightness membrane and how continuity is maintained. The main objective should be to ensure that there is an adequate understanding on site of the air tightness requirements at joints, intersections and junctions of the different wall types, and to ensure that the air tightness specification is met. Once the building is completed it is very difficult to examine the air tightness layer and rectify any defects that can arise. Inspections should concentrate on parts that will be covered in the completed building. The project manager leads the training, coordination and the inspection procedure, also assisted by the design team. Training will include informative briefing. All new personnel working onsite will be updated in the intricate design. Any questions onsite of the materials and detailing will be forwarded to the design team before any more works continue.

4.3 Air tightness details and specifications for Maree N.S.

4.4 Testing for air tightness in Maree N.S

Testing of the building envelope should be carried out before the air tightness layer is covered up. As see in fig----- the air tight layer is located behind the interior wall finish. Testing should begin before the battens and plasterboard is constructed. All new Passive Standard buildings require testing for air tightness as stated by the Passive House Institute. There are a few methods of testing for the different components of the building envelope.

The air tightness of a building can be accurately measured by carrying out a blower-door test. The test involves placing a powerful fan suspended in a canvas sheet within a door opening and operating the fan at very high speeds thereby creating either negative or positive pressure within a building. By creating negative pressure within the building air is sucked out of the building through any gaps or cracks in the building fabric. The Passive House Institute (PHI) states that pressure used for such a test is 50 Pascal which can be accurately set by the blower door equipment. When undertaking the test it is usually quite easy to identify major leaks due to the presence of a strong draught which can be felt by the hand. Any cracks or gaps can be sealed with appropriate materials as the test is being undertaken. Then the readings are taken. Passive Standard is reached when there are less than or equal to 0.6 air changes per hour at 50 Pa pressure.

A fan pressurisation test is putting positive pressure into the building at 50 Pa pressure. A fan pressurisation test can quantify air leakage through the building envelope but it cannot locate the cracks and gaps which may be situated throughout the building. Visual inspection can reveal some of these defects in the building envelope. Carrying out an air leakage audit using either smoke tracers or an infrared camera will identify all the major air leakage paths. Smoke tracers are in the form of pencils or smoke machines. Which when put possible air leakage paths will pull the smoke through the building envelope. There is rarely the need to fill the entire building with smoke.

Air leakage that is associated with a building element or component can be tested separate by pressurisation. The component eg: a particular room of interest within a building is isolated by containing the area within a temporary sealed compartment. This compartment is pressurised and the air exfiltration can be estimated.

Chapter 5 Conclusion

References

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