Finding the chase and cutting to it

Entrances and internal walls.

We’ve looked at roof insulation being a warm winter hat for your home. Insulating your floors has given you a pair of cozy slippers to isolate your feet from cold floors. We can think of doing the same for your walls as giving you a heavy-duty winter coat.

Before I dive in, I want to go through our house as a case study. On paper, building started when building standards were still pretty lax compared to the latest edition. Yet, as a self-build, it was a different beast to our 2000 CE built house.

For a start, the external walls are 30cm in depth – a brick layer, the breeze block layer, the cavity wall filled with rock wool insulation, the plaster lined with foil to protect against infrared losses and gains. Upstairs, the dormers are lined with thick celotex and the lower plaster backed by the same material. Chalet bungalows should be notoriously bad at keeping warm, but our house isn’t.

Our 141m² “proper” house built in 2000 cost around 18,000 kWh in gas to keep warm with a programmable thermostat. Our 244m² chalet bungalow finished in 2012 cost 17,950 kWh in gas to do the same with the same level of controls. Once we tightened up how the heating controls worked, we got that down to 12,950 kWh.

Why did it cost, comparatively, so much less to keep the bigger house warm? Wall insulation. That’s the biggest difference between the two properties.

Internal walls.

This could potentially be a DIY job. To start with, measure the depths of your walls. Ours are 18cm in depth, and like many houses, we have stud walls. In the past, studs were left largely empty. But lining between the studs with materials like celotex (a DIY task), or foam filled insulation (needs to be fitted by a specialist).

Even just applying rock wool (a DIY job) gives real benefit. I happen to know our house has celotex between the plaster, which gives a U-value of 0.21W/m²K.

The U-value measures the rate at which a material transfers heat. It is measure in W/m²K or Watts per (metre squared multiplied by Kelvin). In other words, the energy divided by the area multiplied by temperature. Remember, the lower a material’s u-value, the better. Very few things are close to zero.

But there are other areas to consider. Doors can be replaced with versions with much lower U-value version. Let’s look at an internal solid wooden door. Its U-value is around 2.5 W/m²K. We do have gaps at the bottom of our doors, but otherwise, they are doing a reasonable job. The house does need to breathe before we start sealing up such gaps.

I’ve heard foam spray foam insulation can cause issues with damp!

A reputable company will ensure that all work complies with best guidance, but ironically, air gaps and spaces are required to allow air to move and stop condensation against plaster and internal pipes and wiring. Some buildings may not be suitable for being tightly insulated with foam insulation as a result. The right materials for the right building is essential.

If you can’t swap an internal door for any reason, buying a thick velvet curtain or thermally lined one for the door can dramatically help improve heat retention. Door curtains can be engineered to open automatically when doors open – eyelet curtains attached to the door itself are ideal ways of achieving this for little effort, or more traditional curtains teamed with dormer or door rods.

Such techniques were used in medieval castles, but the right fabric and mechanism for your room can bring this right up to date!

It’s curtains for you, my friend…

A properly dressed window finishes a room. But we don’t just use curtain for privacy. Good quality curtains can dramatically improve the thermal retention of a room when they are closed.

So it is always worth getting thermal blinds and/or curtains. Venetians are great for controlling light, but it is much harder to get ones that have a decent heat retention score.

If buying ready made curtains, thermal linings and pelmets over the top can really help keep in the heat. Team styles with your decor and rather than looking dated and pastiche, you can end up with a clean and modern feel. Light colours not only reflect infrared but visible parts of the light spectrum, helping keep rooms feeling light and airy during a dark winter.

Ready made curtains can be expensive. Teaming up layers can help improve performance and lower outlay: team cheaper thermal roller blinds with cheaper curtains to give the benefits without the cost. In our dormer rooms, I used single curtains from a pair, and a bent curtain rood to allow the curtains to be drawn back against the dormer wall – when drawn, they provide an external layer to the dormer cheeks, which can be difficult to do otherwise. A dormer rod is a more traditional way of achieving the same goal but costs dramatically more.

Coming up in part 2.

This is a big subject, and this part has focused on what could be achieved internally. Next week is all about the outside.