Kitchen extension - what can you do to make sure it stays cool?

[wewearshortshorts]

How do you build for a cooler house?

We are about to start a big kitchen extension and it will include switching from a boiler to a heat pump. There will be skylights and an enormous slide window out to the garden.

What can we do to plan for a cooler house?

Solar glass- an absolute must. And built in blinds.

What company did you use for the fan coil unit?

I have just spoken to the heat pump people about the fan coil unit and they think it won’t work in our house.

Thank you so much for talking me through this.

It seems as though the glazing might be where to put our energy. The bricks of the extension will be exposed, so that might be cooling.

What should the material of the floor be?

Sorry to say but exposed brick is probably less good than plastered as it doesn’t block the heat from outside as well (plaster adds an extra layer of insulation). However if it’s a double layer of brick (supporting walls will be) then it’s pretty good at heat blocking anyway.

If you are having a flat roof, ask your builders to use a light coloured roofing material. Definitely get insulation built into the extension roof, for winter purposes as well as summer.

Flooring - nothing dark as it warms up where the sun hits, but not very light as it will show the dirt! Tiles or concrete will feel cooler underfoot in summer than wood, until they heat up. But if you’re not having ufh, then tiles will be freezing in winter.

Thanks @minipie . We will have underfloor heating.

our patio outside needs to be a porous material so that water can pass through for the protected trees around it.

Sorry - I didn’t mean to post then! I was going to go on to say that I had been hoping to match the kitchen floor with the outside patio.

The kitchen is likely to be 4 metres tall. Does height help with cooling?

Do you need enormous doors and windows? A bit of a cliche, expensive and heavy, and the main source of heat in summer unless they are north facing - and then they will be cold in winter, unless triple glazed (and even then...)

Think about what the bottom 1/4 of the doors and windows are doing. Are they letting in light? Not much compared to the top..mainly lighting the floor. Are they increasing the view out - only of the immediate bit of the patio. Are they letting in the summer heat - yes! And the further down the glazing goes from any shading, the further out that shading has to reach to be effective. Making the room darker....

Don't oversize skylights either. And ensure they are fitted with a retractable blind (they are made of a sort of reflective mesh).

If you are having ufh this is perfect for cooling as you have a large surface area which means you can get the heat pump to supply water at say 19 deg which will cool you down but hopefully not form condensation.

But you won't benefit much from cooling if too much heat is getting in, there is only so much a domestic system can do.

At 4 metres, are you putting in a ceiling fan? And some sort of ventilation at the top to create a chimney effect and draw heat out at the end of the day.

My brother (south of france) has the same slab of flooring on his patio running into the house. It traps the heat and sends it inside. Not the best idea if uou are looking to cool your house

We are planning a multi pronged attack 😅 So rooflight that can open (instead of our originally planned lantern), French doors instead of bifolds, air con unit, outside we are going to fit either an awning or a pergola / awning over the patio so the back of the house gets shade. We are S facing in SW London and the last few summers have been unbearable. Hoping these will all help.

Definitely a ceiling fan. What would the ventilation be to draw out the heat?

I can see that would be a mistake.

Did they say why a fan coil unit wouldn't work? They are a fairly simple piece of equipment. Our heat pump people hadn't fitted one before so make sure there's a factual reason it won't work for you rather than a lack of experience.

The brand of ours is Jaga (from memory)

The picture in my mind is a window up high with an automatic opener. It needn’t be big.

@TheSandgroper is that more effective than a 3m door that entirely slides? Is it better to have the glass doors shut but an opening above?

@wewearshortshorts In a 4m room with 3m doors, I would look at putting another layer of windows over and making them open a bit. The higher opening, the more warm air is expelled and the more the flow through of air.

Also, a small, high window allows for flexibility. You won’t want to go to bed with your sliders open but a small, high window would be fine. If you are putting in a velux that opens, you probably wouldn’t need what I’m suggesting.

I wish we'd got the bifolds/veluxes with blinds built in.

This all sounds sensible. See if you can get an external blind on the rooflight too. We have retrofitted them to existing veluxes and they really make a difference. We (DH) needs to get up on a tall stepladder at the start and end of the summer to close/open them, as the ones we got are manual..I guess when he's too doddery to do that we'll have to finally move 😅