Insulation, is not the answer, STOP getting hung up on lowering U-Values, this is NOT the most IMPORTANT element when it comes to reducing energy bills.

A strange notion coming from Passive House architects, I hear you say.

After getting the design right ie orientation, solar shading, what is the most important element?

Having ‘grown up’ in the industry during the rise of energy efficiency, we thought increased insulation = increased energy efficiency = warmer building.

And this is true.  To an extent. But it will cost you more to highly insulate your building.  And likely cause overheating – which then causes its own problems, where we may need air conditioning, which means more energy use.

When designing a passive house, insulation and u-values are the last thing we consider spending money on.

The most important element to get right in your building could also be the most cost-effective.

Airtightness.  And the bonus? It doesn’t cost much to get right; just careful detailing, workmanship and understanding by those on site.

Think about it: Have you ever been to Spain, or somewhere, and it is really hot? Then a nice breeze comes along and cools you down. This is what draughts do in your home; cools you down.  Which results in less thermal comfort, your building feeling colder, which often leads to complaints of cold, and subsequent turning up of the heat.

We recently re-calculated 3 of our passive houses, changing only the airtightness; changing the airtightness to Northern Ireland regulations. This increased the heating demand by 430%. In reality, the increase in heating costs will likely be higher due to the draughts. Not addressing the airtightness is like leaving a window open all year round!!

An important side note: with airtightness comes the need for MVHR; otherwise you are creating problems.

Feel free to get in touch if we can be of help.