How air-tight is your home?

A webinar by Diane Hubbard from the Carbon Coop.

So, why does air-tightness matter?

Well, if a house is not insulated properly or has draughts, cold air can move around the insulation so that its not effective. And, if warm, moist air is escaping through areas you don’t want it to it can condense on the building fabric eg wooden joists and cause damp and mould. Draughts will also disrupt the performance of any ventilation system you do have – giving poor ventilation. This is particularly problematic with Heat Recovery systems.

So, what can I do about it?

There are four stages:

  1. Know where you are starting from
  2. Set your target
  3. Develop a strategy
  4. Monitor workmanship and quality of work on site

1. Know where you are starting from

Use the blower door test to measure the air tightness. In Bristol, and now in Bath during the winter months you can get a survey from The CHEESE project (Cold Homes Energy Efficiency Experts). This gives a thermal image of your home showing where all the cold spots and draughts are.

There are lots of different problems that you can encounter, but these include:

  • In newer houses this could be dot and dab plasterboard – where cold air can filter in around the dabs, older houses tend to have continuous plaster
  • In older houses, areas where the plaster is not continuous eg poor junctions between wall and ceiling, ceilings and floors around the skirting board can let cold air in or warm air out

2. Set your target

You can either pay someone to do this for you, or you can use the Passivhaus Planning package, which costs about £100. This allows you to play with different solutions on a spreadsheet and look at the impact on your home.

To help you decide you need to be clear whether you are just trying to get rid of the worst draughts or going for an Enerfit standard (highest level for existing buildings). This will also be dependent on the budget you have.

It is key to get this right from the start, because it is almost impossible for builders to deliver good air tightness if it hasn’t been designed in.

3. Strategy

This is about how you are going to get to your target and getting the specifications and design right. At this stage, you will also need to design in an appropriate ventilation system so you can manage the air-flow within and through your home, see the Draughtproofing v. Ventilation training summary here.

What will be done and when, by whom and for how much.

4. Quality of work on site

Work with a builder who understands what you are trying to achieve. Appoint an air tightness champion, but ensure that everyone on site is working to clear specifications to achieve the target you set at the start.

This was a really useful explanation of the importance why you should improve the air-tightness of your home and a good overview of how to achieve it.

The slides and the link to the video recording of the webinar are below.