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Leaking buildings are the biggest single waste of energy for most UK buildings
Infiltration or air leakage can account for up to 50% of heat loss in modern homes & increase C02 emissions. It has long been established that ventilation is an absolute & essential part of creating a healthy, comfortable, energy efficient home.
Unfortunately, infiltration (unwanted ventilation / uncontrolled ventilation) or air leakage means that expensive heated air can escape from our homes, wasting valuable energy. This has an expensive, ever increasing premium that is hard on the pocket and hard on the environment. It is a fact that air (energy) leakage is one of the most significant contributors to inefficiently heated homes, which inevitably leads to significantly higher levels of CO2 emissions, not to mention costly waste.
The more we insulate our homes; the impact of infiltration in relation to reducing the performance of the building envelope is drastically increased. Infiltration or air leakage can account for up to 50% of heat losses in modern homes which in turn also leads to significant reductions in the durability & viability of the structure, not to mention the health & comfort of those who live in them.
Reducing energy requirements, energy costs and CO2
Research has shown that approximately 50% of the energy consumed in the UK goes into the servicing of buildings, of which 60% is used for water / space heating and cooling. A reduction in our reliance on energy in the area of servicing buildings has the highest potential for making the most immediate impact for a reduction in CO2 emissions and energy use.
While the recent government initiatives in the area of supporting the uptake of renewable energy are to be lauded, the performance of such systems is entirely dependent on the quality of the fabric of the construction.
It seems obvious that one should place emphasis on ensuring a properly installed, quality insulation is fitted in the external envelope of the building, and of course, that the building envelope is effectively draught proofed or in other words, Airtight. However, this is not the case in the majority of homes we build annually.
Modern, low energy buildings, be it Canadian Super E, Passive Houses, German Low Energy Buildings or any other energy efficient construction, individually and collectively place Airtightness as a primary part of achieving a low energy building.
It is really about time that the UK construction industry followed the lead of these innovative methods of low energy construction, if we are to truly prepare and face up to the looming energy and environmental crisis, and build homes that use significantly reduced amounts of energy. In the past it was very clear that a lot of heat loss through the fabric of the building envelope was as a result of the installation of little or in some cases, no insulation and a very low level of draught sealing of the building envelope.
Priority in our building regulations was placed on achieving lower, and lower U-values for each elemental area of the building fabric. This inevitably leads to lower levels of heat loss as a result of an increase of the insulation. However, the proportion of heat loss as a result of uncontrolled air leakage through the external envelope of the building has yet to be seriously addressed. Air leakage allows expensive heated air to escape from our homes and buildings.
Therefore, the most cost effective means of reducing our heating bills and increasing energy efficiency in our homes is to decrease to level of uncontrolled ventilation in the living space. The only way to ensure this, is to build a fully and properly airtight structure, even if it is an extension to an existing building.
Airtightness creates a comfortable, healthy internal atmosphere
Airtightness also lends itself to a comfortable, healthy internal atmosphere, within the living space and ensures that the building fabric can breathe and is maintained in a healthy condition. This is especially achievable with the Pro Clima Airtight System which utilises a ‘world first’ intelligent membrane, that manages the inherent moisture out of the structure of the building, even after the building is complete.
A lack of airtightness dramatically increases the risk of mould growth and structural degradation, particularly in light weight construction, leading to costly structural repairs, necessitated by the development of mould, rot, damp and condensation. This is as a result of the warm moisture laden heated air in the living space, penetrating and rapidly condensing within structural elements.
Airtightness for intelligent moisture management
Levels of Airtightness can be achieved by sealing the building envelope by using Vapour Barriers, Vapour Checks, wood based panels (e.g. OSB and plywood)’
or by plastering, porous concrete block work. These methods of achieving Airtightness have their limitations and do not have built-in Structural Protection or Moisture Management abilities, especially if the structure has a high vapour resistance on the exterior side of the construction.
The Pro Clima Airtight System provides intelligent vapour checks which are humidity variable and vapour permeable (e.g. Pro Clima INTELLO+) and a complete solution to potential problems associated with the requirement for airtightness. Pro Clima also provide a complete range of non-toxic specialist tapes (designed for every construction detail), adhesives, sealing solutions and intelligent membranes to ensure a building is airtight and healthy.
Moisture can enter structural elements. The more we seal our building envelopes, the greater the need to control moisture levels in structural elements, especially in buildings which are very vapour-tight on the external side of the building fabric and particularly in timber built constructions or timber sections of masonry constructions.
- Moist laden building components (e.g. insulation or timber materials exposed to high moisture levels on site),
- By diffusion (e.g. the installation of inappropriate Vapour Checks which do not have the required vapour resistance),
- By means of moisture laden heated air leaking into the building fabric and rapidly condensing (e.g. Leakages in the overlaps of the Vapour Check or service leaks).
It is impossible to eliminate with certainty the risk of moisture build up in structural elements. The only solution is to install Intelligent Membranes (e.g. Pro Clima INTELLO+)
The world-First Intelligent vapour check, first for airtightness, energy savings and moisture management INTELLO+ is unique in that it regulates (out of the structure) the moisture trapped within structural elements even after the complete building envelope is sealed air tightly, even in constructions which are extremely vapour impermeable on the outside. (Inlus), to seal the building envelope as oppose to regular vapour barriers and foils traditionally used.
Rather than achieving temporary airtightness with unsuitable tapes and adhesives, quality, durable tapes, adhesives and sealing solutions should be used. Pro Clima provide a range of proprietary airtight sealing tapes (e.g. Vana Tape for sealing overlaps of the vapour check and patching, Tescon profil for sealing reveals to name but a few), adhesives and sealing solutions, that are designed to simplify the sealing process in a cost effective way and ensure a durable seal is maintained. A vapour check provides a very high safety factor, for constructions, against moisture induced structural damage and mould growth.
Once the airtight building is complete it should be viewed in the same manner as one would view a gas pipe or water pipe, it shouldn’t leak on the first day it’s tested, it should maintain an airtight seal for the lifetime of the building and any leaks incurred in the building envelope should be resealed. During winter months INTELLO+ acts as a very effective vapour check and protects the structure against warm moist air diffusing through the membrane into structural elements.
So where does all the energy go?
To achieve full and proper airtightness, it is most important that all gaps in the building envelope are effectively sealed, particularly in lightweight constructions. Gaps in the envelope may occur at overlapping junctions of the Vapour Check or Barrier which are not sealed correctly, services penetrating the vapour check or barrier, or at junctions between the building envelope, in particular windows and doors. Leakages in the building envelope can be characterised into two categories:
- STRUCTURAL LEAKS – These are leakages that occur at joints in the building fabric and around reveals (i.e. windows and doors). Structural Leakages often occur at down-lights, loft hatches and separating floors in particular.
- SERVICE LEAKS – These are leakages that occur where pipes and cables penetrate the external envelope of the building. These can be soil pipes, water pipes, extract vents to name but a few.
The most significant leakages can often be a combination of both structural and service leaks in the building envelope. Air moving through penetrations in the building envelope can also result in hidden moisture in the construction, which, in turn can lead to condensation, mould growth and building damages. If moisture laden warm air (i.e. energy leakage), penetrates structural elements from the inside this may cause long-term damage to the viability of the structure & generate increased, life-long heating costs, placing huge demands on energy resources.
In the winter, the warm air escapes, the cold air leaks in to the structure and the heating bills rise. In the summer, the opposite happens, warm air leaks in and cool air leaks out, leading to overheating and great discomfort for the inhabitants. Even in the case of refurbishing or adding a room, it is important to tighten the building envelope as much as possible.
Build tight: ventilate right
An Airtight building lends itself to a greater degree of comfort for the inhabitants. Airtightness is also a precondition for effective sound insulation, consequently, benefiting from greater levels of sound reduction from the external environment. To maximise the thermal performance of a construction and to ensure the air in the living space remains healthy, some form of controlled ventilation is essential.
This can be in the form of mechanical ventilation with heat recovery or some other form of natural ventilation. When it comes to Airtightness, “Build Tight, Ventilate Right”, is the only mantra to ensure we improve our buildings, while also reducing this shameful, expensive and un-necessary energy waste.
How to achieve airtightness?
There are three key steps to achieving airtightness in any building type.
1. Design for Airtightness: To maximise the Airtightness of any building the Designer/Architect plays a pivotal role. Airtight details for common leakage areas which are difficult for the builder to seal on site can be greatly simplified leading to vast improvements in workmanship. Consequently, superior levels of Airtightness can be achieved and of course significant savings can also be made as a result of time savings on-site, at the installation stage. The Architect can also specify materials and propriety Airtight Sealing Products which simplify the Airtight sealing process for the installer and guarantee a clean, durable and lifelong seal.
2. Build for airtightness: When the building is at the construction stage communication between trades is absolutely essential. It is also essential that the airtight installer maintains a high level of consistency and consciousness to continually seal the airtightness layer at a premium level.
3. Test for airtightness: After the building has been sealed for Airtightness the construction must be tested to identify the level of airtightness achieved and also to identify leakages in the building envelope. An Airtightness Test is carried out by a Blower Door Fan, A Blower Door Fan is installed in an external door of the building and this either pressurises or depressurises the whole internal volume of the living space. This test will quickly provide a measured Airtightness Level for the building, and identify leakages in the building envelope.
The importance of getting it right
In the UK it is now a mandatory requirement to carry out Airtightness Measurements on all buildings to a minimum level, as stated in their revised building regulations. The implementation of Energy Performance Certificates (EPC's) for all buildings has placed more emphasis than ever before on addressing the high level of heat loss, directly resulting from a lack of Airtightness in our homes.
The calculation tool used to assess a buildings energy performance (SAP - Standard Assessment Procedure), now dedicates an entire section to heat loss, associated with uncontrolled ventilation. However, it is somewhat disconcerting that in this section one has the option of inputting ‘Measured Airtightness Results’ from a blower door test for a building; or to input a default airtight value, depending on the building types.
While this is in some ways positive, in that it highlights the importance of achieving a certain level of airtightness, it is unfortunate that Airtightness Testing has not been identified as a mandatory requirement for achieving the pre-stated values. As one has the option of entering default values this will simply allow the user to over-ride the absolutely critical requirement for Airtightness, which is the most important structural element to truly reduce the energy-in-use in the building. If one inserts a default value for achieving Airtightness, it should be stressed in the SAP calculation that measures should be taken to achieve the stated default Airtightness Values. An Airtightness Test not only identifies leakages in the building envelope, and provides an exact measurement of the level of Airtightness in a building. It also forms a critical link in the chain of command, from theoretical calculated values for thermal performance and uncontrolled ventilation, to on site practice, which is so badly needed on building sites around the country.
Airtightness Testing leads to better on site work practice, communication between onsite trades, significantly and critically improved energy efficient design, not to mention the additional benefit of much required, quality control, to building, in general.
At what cost
A gap in the buildings Airtightness layer multiplies the energy consumption for heating per m2 many times. An Airtight building not only lends itself to tremendous reductions in CO2 emissions, it also leads to a more healthy and comfortable home for the homeowner and a greater level of confidence and trust in the builder, leading to a win-win situation all round. Intelligent Airtightness, such as that achievable through the Pro Clima System, can be achieved at a fraction of one percent of the total build cost and allows for significant savings to be made on energy costs and potential structural repairs, through-out the lifetime of the building.
Part L of the UK building regulations has been focused for some time now on increasing our insulation levels throughout our homes. Of course, the addition of more insulation in our homes is a critical element to reducing fabric heat loss. However, there comes a point where it would be much more effective to focus on reducing heat loss as result of uncontrolled ventilation in our homes.
A sufficiently airtight home is the only way that ANY insulation, can actually work to 100% of its ability. Thankfully, currently there is a justified focus on renewable energy sources for our homes and offices. This is to be commended. However, if the building is not Airtight, the energy, still escapes, in many ways defeating the initial purpose. Until our building regulations seriously addresses this issue, a lack of Airtightness will always be the primary leak in our heating budgets, causing un-necessary energy loss, strain on our pockets, potential structural damage, and additional environmental damage in a time of precarious balance, not to mention the negative impact on our own health.
Thanks to Niall Crosson and Ecological Building Systems for compiling this guide.