Finding the chase and cutting to it

Unusually, I got thermodynamics in physics. Heat is all about vibration of molecules rubbing together or hitting each other. Small amounts of friction taking and giving off energy.

Which brings me to today’s subject. It is inspired by a throw away comment my husband made this morning. Would the recent heat waves would change the priorities of home builders in the UK, i.e. build them to keep them cool as well as warm?

I live in a temperate country, we have seasons. The things that help us keep warm in the winter are terrible for keeping us cool in the summer. I’m talking of the principles of solar gain, trapping heat indoors, and heating via hot water,

Except one of those. Trapping heat is actually a preventative measure in keeping cool. Good insulation is terrible for losing heat, but if you maintain your thermal envelope, a room can keep up to 5°C cooler than outside. This is how many architectures work in deserts and the tropics. Long before chemical and mechanical heat exchangers were used.

If we look at how more traditional methods work, we see highly efficient and mechanically simple designs appearing all over the world. Carpets are not placed on floors in Middle Eastern countries but are used as a barrier to prevent the heat stowed in the wall material from heating the air in a home during the day. Exactly the same idea as cavity wall insulation in a modern UK home.

I’m not hanging carpets and rugs up on my wall this weekend!

I’m not suggesting you do. I am saying, appreciate that you may be lucky enough to have some help already built in to the fabric of your home.

What about solar gain? I have to say I’m closing my blinds and curtains but it’s not making much difference!

You have to combine it with other passive measures. If you have good insulation – once the heat is in there, it needs a channel to escape from.

Let’s look at our bedroom, it faces due south so bakes in the afternoon sun. At 20:00 last night it was 30.2°C.

I opened the windows at 20:25 (east facing and south facing) in the room and the temperature got down to 26.8°C by the time we got to bed at 22:30. Because we’ve been using this approach regularly, we are now comfortable sleeping that warm. We have a flat sheet between us and the world that helps our bodies wick sweat away. My skin temperature is maintaining its usual levels. According to Samsung Health, my sleep is off good quality.

We are not even using a fan at the moment, overnight. Our offices are the only places where we are using such devices: the office machinery driving up temperatures during the day.

But that still sleeping in a room whose air temp is 26°C!

That is 9°C warmer than the WHO recommends for most people. Actually, for older adults the recommendation is up to 25°C. We are heading to those warmer temperature needs.

But my husband’s comments are valid. Air to air heat pumps providing “heat and air” would give the UK inhabitants the freedom they need to respond to the weather.

Retro-fitting is non-trivial. To prevent heat channels (both losses and gains) and condensation paths, such measures need to be built in to the fabric of the structures. As they are in office blocks.

Not what you are doing today then?

Like many, we’re looking at fabric blinds to shield from the sun over the summer. Our triple glazing will give us insulation during the winter, But if you lack triple glazing, external, insulated shutters can boost your U-values for your windows and doors.

Our sail downstairs helps to protect the lounge from direct sun in the day time.

We then use passive cooling to remediate any gains made. All for significantly less than running air-con in terms of installation, running, and maintenance costs.