Air tightness in new homes is increasingly becoming a hot topic with Part L of the building regulations changing later this year, developers, builders and self builders will need to improve the air tightness of their new homes to help in passing SAP calculations. We shouldn't however look upon having to make our buildings less "leaky" as an extra burden placed upon us by the industry regulators but as a benefit and a route to improving our buildings operating efficiency. After all the we have paid for the air within our dwellings to be heated, why should we let this warm air escape through our building fabric uncontrollably ? At Buidakit we believe that air tightness in dwellings is a good thing. The air tightness of your building needs to be planned at the design to maximise the potential gains. below is our guide to planning your air tight build.

• Consult with the professionals at the early stages of building design. Sit down with your building designer and discuss a strategy. This may involve an energy advisor and other consultants if necessary. Agree on a airtightness figure that will be entered in the design stage SAP calcs.
• Choose you preferred method of building to assist you in achieving your agreed figure. All Buildakit's building systems are capable of achieving extremely air tight buildings. SIP panels are the obvious choice for an air tight building due to their solid facings, sealed joints and detailing between panel junctions. That being said though there is no reason that a Timber frame building shouldn't be as air tight as a SIP building. As a matter of fact, the most air tight building that we have supplied was actually constructed using timber frame and achieved an air test result of 0.8. Its simply down to the detailing and the methods that are used to build the air tight layer.SIP structures are made airtight by their nature no extra effort is required to make the building airtight. Air tightness is usually achieved in timber frame using a Vapour Control Layer and more planning and attention to detail when installing the VCL and education of following trades is required to make these buildings airtight.  
• If your planning on an air test result of 3 or less you should probably consider a mechanical ventilation system to ensure the well-being of occupants of your building. this should be planned in the early stages of design - before the timber frame or SIP structure is designed (pass this design info to your timber building designers so duct paths can be designed in) . This will ensure that ducts are run in the most effective way and that air flow within the ducts will not be restricted. Of course your ventilation system should have heat recovery, after all you want to throw away as little heat as possible. There are systems on the market today that are 85% efficient or more. Mechanical ventilation also has the benefit of filtering the intake air which can have a benefit to the occupants health (asthma, allergies etc). These systems are not overly expensive, and self builders note, that the ducting is easy to install and can be done yourself.

In summary then, there is much more to consider when planning an airtight build but these few pointers should get you started in planning the airtightness of your home.  Above is an image of a Buildakit Hybrid home, the airtightness in the external walls is achieved using the SIP system where as airtightness in the attic truss roof structure will be achieved using a polythene Vapour Control Layer. The house will be fitted with a mechanical ventilation system. I will post the as built air test as soon as i have it.