Finding the chase and cutting to it

Last week, A Coat for the House, Part 1 looked at what was going on internally in your property. This week, we’re heading outdoors.

External doors, windows, and walls.

Entrances and exits.

Entering with the front door, we can then go to the other entrances/exits, the windows and end up with the walls.

Poor quality front doors can leach heat. As a result, all types of door quote their U-Values, If you are in the market, it is worth shopping around for a product that works for you. A front door typically has a thermal rentiton of 1.0 – 1.4 W/m²K, though a top of the range one can get as low as 0.7-0.8 W/m²K and typically has Passivhaus certification.

Door curtain can be used to boost the rating of a typical door: keeping the curtain colour the same as your hallway palette can give a high end feel, as well as keeping the heat in.

Of course, any external door can be treated the same way to similar effects.

Windows

Windows are the next factor. If you have single glazing, the U-Value is around 5 W/m²K.

Any double glazing fitted between 1970 and 1990 typically has a U-Value of 3.0-3.5 W/m²K, and ones from 1990 to 2000 has a rating of 2.7-3.0 W/m²K. Today those values have improved to 1.2-1.4 W/m²K. So it is worth looking at whether your units could be replaced.

UPC glazing does fail over time typically within 20 years. Any window fitted in 2000 will need to be replacing before 2030, so if you can, make a budget to make that happen. Anything older has probably already failed.

Different technologies have helped make that difference, including films to reflect light and heat back into rooms for example. Triple glazing is not a huge jump, coming in at 0.6-0.9 W/m²K or a Passivhaus certified one achieving 0.5 W/m²K.

Walls, the final frontier.

Whatever your style or age of house, solid walls make up the majority of the fabric of your house. It is the hardest to treat once the building has been constructed.

Cavity walls.

In the 1920s, the UK started to introduce cavity walls. This was a modern technique whose aim was to keep our moisture from British domiciles, a protective layer against our wet weather. It wasn’t until the 1970s that insulation was added to such walls and by 1990, cavity wall insulation became a compulsory part of the building standards, first with polystyrene (often balls), then with rock wall, celotex, and finally foam.

How do I know if I have cavities and why bother insulating? More heat goes out to the roof!

If your house was built post 1930s, it is worth checking if it has cavity wall and if that space is insulated. If it has and doesn’t, get it done as soon as you can: that insulation can reduce your heat loss by 80%. The U-value for an uninsulated cavity wall 1.5-1.6 W/m²K. A wall with a U-Value of 1.5 W/m²K wall loses 30 W of thermal power per metre. Over a day, that is 24 * 30 Wh, or 720 Wh. If the wall is 6m2, that is 4.32 kWh – if you have a gas boiler, that would need to burn 5.4 kWh in gas to replace that heat and keep your room at a constant temperature. Using that number against the size of your house can help you work out your payback.

Size of external walls in metres x 24 x 30 W = thermal loss Wh x 1.25 / 1000 = amount of gas to buy to keep a constant temperature kWh.

This is why wall insulation is so critical. You don’t need an air pump to get a good EPC certificate or reduce your carbon footprint or save you money. Effective wall insulation can do all that for you. Grants exist if you are a low earner or get other benefits. There are schemes for older home owners and tenants too.

Likely costs are subject to your location in the UK, accessibility and the size of your property. Convert your wall area into kWh of gas and multiply by the cost of the gas to get the ‘payback’.

House type	Minimum cost	Maximum cost
	Minimum cost	Maximum cost
Mid-terrace	£600	£1,200
End-terrace/bungalow	£700	£1,500
Semi-detached	£1,000	£2,500
Detached multi-storey	£1,500	£3,000

I get it, but my house, like great teeth, has no cavities!

Cavity wall insulation is not an option for you. What ever you do, it is likely to cost more and will need an experienced firm to help you do achieve insulated walls.

Often it involves internal or external application of foam or rock wool, with moisture protection and air blocks applied. If you are in a terrace or semi, see if your neighbours would like to team up, especially for external walls.

You may need planning permission. But this is worth doing and newer materials mean that applying internal insulation does not need to take as much space to get great results.

Or consider approaches used elsewhere in the world. Carpets were used in the Middle East to keep warmth in and provide decoration. Can allow wall materials to breathe and keep moisture free, and prevents condensation.

Bringing it all together.

Our coat for the house has many layers, but hopefully there is something here that helps you.

Remember, every bit of gas or electricity you don’t need to keep warm, reduces your bills and your carbon footprint.

This is the last part of investigating the options for insulating your home before the UK winter closes in. I hope you’ve enjoyed it.