I’ve been hearing a lot lately that we need to go above six stars to improve our houses. This sounds like a good idea but it won’t fix the problem.
The problem is that our houses leak air. I have previously likened our houses to leaky buckets, and have also blogged about the fact that ‘no amount of insulation will keep a drafty house warm.’ Air needs to be contained before it can be controlled.
If we build a leaky six star house it is still six stars. If we build an airtight six star house it will obviously perform far better but it will still only be six stars. The simulation software that we use to determine a star level does not offer the capability to specify or adjust the airtightness of the building envelope. Without this capability we are just assuming that everything is OK. Everything is not OK. The stars don’t mean much, and the R-values and U-values don’t do much if the house is leaky.
So where’s everything going wrong? It’s all about our control layers. Water, Air, Vapour and Thermal……in that order. The problem is that we think about ‘Thermal’ without considering the three steps that should happen prior.
We think that we’re doing a good job with ‘Thermal’ but we’re not. We install insulation very poorly, and as I have mentioned in another post, a fair percentage of our thermal envelope isn’t even insulated.
Thinking that we are doing a good job thermally we are now even considering WUFI simulations. A WUFI simulation deals with vapour diffusion and assumes that we have an airtight envelope. Our mainstream buildings aren’t insulated properly for a start and aren’t even close to being airtight. If the wind is whistling through the building fabric, vapour is not nearly ready to be addressed.
How about the ‘Water’ layer? Are we doing a good job with that? From my observation on building sites it seems that the wall wrap is primarily used just to hold the insulation up. Joints in the wrap are not taped, connections are not taped, penetrations (including windows and doors) are not taped, and tears in the membrane are not repaired……… the membrane is not exactly capable of keeping water out so it’s not a weather barrier, and it’s certainly not an air barrier.
Let’s look at the list again and see how we’re doing.
- Water – Not waterproof.
- Air – Not airtight.
- Vapour – obviously a bit irrelevant given the state of the two items above.
- Thermal – poorly installed and won’t work unless items 1 – 3 are done properly.
This is a pretty poor report card and it’s all because our energy rating system begins and ends at number 4. By only dealing with number 4 we are ignoring other issues and unintentionally causing other problems such as condensation, mould and structural decay just to name a few.
The other problem is that even if we did address items 1-4 it doesn’t help that the energy rating is only in report form and is not required to be verified on site. We can be as knowledgeable and well intended as you like in writing a report but it all amounts to nothing if our advice doesn’t eventuate in the built form.
So what’s the answer? Implement a 1234 strategy with everyone involved in the process. It is important for everyone to know how to do it but it is more important that they know WHY to do it. You will find that once trades know why they are doing something they begin to offer suggestions to improve the system. These types of conversations are enormously beneficial. Verifying implementation along the way and testing with a blower door plus thermal imaging will ensure a optimal result.
One last thing. Ventilation. If you are implementing a good airtightness and insulation strategy, ventilation is a vital component and must be considered. I have briefly blogged about ventilation before , (click here) and I will dedicate another post to this subject in the future.
As you can see, there’s more to building performance than star ratings and R-values. The good news is that we don’t have to wait for regulations to change in order to do things better. We have the know-how and strategies now to create safe, healthy, durable, comfortable and energy efficient buildings. Just get the team together and make it happen.