Insulation can be a poison chalice – if you leave it to the builder

Ask a builder what insulation they think you should use, they’ll say PIR (brand names: Celotex, Kingspan). It may be the only insulation they’ve used. It’s what they were taught to use. It’s easy to get hold of – so they can just pop down to the builders yard and pick some up. Above all it’s familiar.

But there is a problem:

It will leave your home hot and sweaty on hot summer days and cause condensation in winter.  

The reason for this is twofold:

1.     It is made of plastic so can’t manage the moisture in your home. And you are so good at creating moisture - just by living. End result: damp walls and mould.

2.     It has low thermal mass so can’t hold the heat and stop it coming into your home in summer. End result: within a couple of hours, your home is as hot inside as it is outside.

You are the key

There is an easy answer to this – and it’s YOU. As the homeowner, you’re the one to decide how your house should behave and the materials you want the builder to use. Yes, it means you need to get involved. No, you don’t need to be an expert. You just need the basics so you can ask the right questions and get what you want.

What is the information I need?

You need to understand that all insulation is not created the same. Plastic will always cause your home to be sweaty – anything left in a plastic bag will get sweaty and mouldy – and your home wrapped in PIR will be the same. It’s because fresh air can’t get in and moisture can’t get out. There is a time and a place for the use of plastic, but insulation is not it.

Natural materials can manage moisture. It is absorbed into the insulation and keeps moving – either leaving the building completely or released as the room dries out.

And here’s the big one:

Natural materials will not just keep you warm in winter, they can also keep you cool in summer. This is because they heat up very slowly, so they contribute to a long Decrement Delay – the time it takes for the heat outside to be replicated inside.

·      For PIR this is two hours.

·      For hemp, wood fibre and recycled denim you’re looking at nine hours plus.

This is the just the tip of the iceberg

There is so much more to know about these materials. They’ll add value in ways you can only imagine right now. So don’t leave the builder to make all the decisions. Join the team. Educate yourself enough so you know what you want. And get the home you deserve.

If this makes you think, ‘I need to know more about this retrofit / renovation game before I make decisions I might regret’, take a look at Beginner’s Guide to Eco Renovation and What the Builder Won’t Tell You.