Overtime builds have become well protected, the volume of heat that has decreased is drastic. This is also for builds that are constructed to a minimum within the building regulation. In relation to this, the quantity of heat misplaced through unrestrained air leakage has increased. If you are a builder who wants an energy efficient build, it's vital to understand this. There are loads of new build homes that don’t perform, compared to how well they are designed. This process is a performance gap, from this the major problem would be poor airtightness.
As for existing builds, the best way is to seal as much as possible around the house, as it would be difficult to reconstruct certain parts. Below will give a depth idea of making a home more airtight, but for existing if you read (How do you check for air leaks? and How do you find an air leak in a building?) These will help you make your existing home airtight, but if you are building from new or even want to learn more, continue reading.
When it comes to air leakage, you would think of air flowing through the home, but there is more to it, making the process very complicated. Wind can produce positive and negative pressure towards the build, which would push air in and suck air out, creating a pressure differential.
Air leakages usually occur at junction paths between different materials of a building. There are materials that are airtight, but there can be others that need an extra layer. These leakages occur at chimneys, ventilation bricks, penetrations of materials, pipes in kitchen and bathroom, electrical sockets and around lighting etc.
When it comes to design and creating, it is vital to understand an air barrier line around the build this would-be roof, walls and floors. You could say it is comparable to a thermal envelope, which provides insulation for the boundary.
It is mostly common that internal air barriers are used in the UK, but these do have many penetrations which require specific parts. The barrier will need an extra coat to be laid at certain areas, but for those areas that are not needed, it will be adequate. A great example would be (OSB), known as oriented stand board. This material is fairly airtight, so when fixing ensure you seal properly at the joints of the boards.
Like most products, there are always different variations, meaning you can find a more airtight product of an OSB. That is why it is important to add or remove details and products used for a build, also for existing, if you want to add or remove to create better airtightness. When looking for specific components to construct when it comes to airtightness or even sound insulation, it will provide you with the information that the item is used for more air tight or its more sound proof.
Concrete is a higher product that blocks air paths, so there will be no need to add extra layers around this material. Masonry can also be developed into a more airtight product. All you need to do is apply a thin layer of mortar. ICF, known as insulating concrete formwork, is also a good airtight material.
Buildings are intricate designs that provide many structural networks designed for walls, floor and roof. Where these complex junctions are is where most of the air would travel through. So, it is ideal to get these details cautiously done, so that you can achieve good airtightness. The main idea is to ensure that there are no gaps or cracks in any building fabric where air can penetrate and flow through.
When it comes to comfort within our homes, we require fresh air to breathe, and also get rid of odours within a home. The build also needs to breathe, then be just air tight, so (Approved Document F) of the building regulations would help you understand the dynamic between the two.
You may wonder why seal up the place, when we will cut holes to fit a satisfactory ventilation system. Even though it is a great question, we also need to understand that we are trying to reduce uncontrolled air leakages within the build.
Once creating an airtight build, fresh supply can therefore stay delivered through controlled paths to every room. If you are building a more efficient build, this being a passive house, then heat lost through controlled ventilation will have problems. If there are recognised paths, then heat should be restored from the ejected air and used to pre warm the incoming of the fresh source. This would usually be done by a (MVHR) system, known by mechanical ventilation and heat recovery.
When installing an MVHR system, it will only save energy when the airtightness of the build is less than 3ach@50Pa. The reason for this is that electricity will run the system, and if there’s too much air leakage, it can interfere with the system, causing energy problems within the home.
To obtain a good airtightness is planning barrier lines at design stage, as well as actual construction and following the plans in detail. Otherwise, if they are not followed, there will be gaps and cracks that builders would leave and not bother to change or repair. Trying to get this process done would be difficult if communications between design and contractor aren't right.
It is key to get these requirements dealt with straightaway then later during the build stage as it could cost money to change if not done correctly and could cause leakages. It’s ideal to take your time and get it right, then rush it, and then problems start to happen.
Another design and build process that airtightness could cause issues is when rafters are seated on a ridge of a beam. What can be done is put a strip of membrane over the beam before placing the rafters. This would be easy and fast for a later stage, but would need to be done as the roof is in place.
Majority of builders would know about this, but it is important to just go over so they understand that when it comes to building, all junctions and materials with connections are put and sealed correctly.
Mainly builders wait till the final stage to do an air pressure test, but if you are not sure of your build and want to check before you can book a pre-test, this would be at an early stage. This can be beneficial, as it can tell you where the problems are before the build's makeup is applied, otherwise it can be difficult to seal depending on the build’s quality.
For an existing build, you can try methods to locate these leakages. If you read locating air leaks, this can help you identify them and get to sealing straight away. There is also a guide to how to seal these leaks. Hopefully, you can follow and understand, but if you are unsure, please contact ATSPACE and we will be happy to guide you through these issues.