Would you install air conditioning in a dormer loft conversion?

[Homerenos1]

We are getting a dormer loft conversion in the summer. 1930s semi-detached so will become 3 storeys.
In two minds on whether we pay extra for aircon.
Anyone who has or hasn't installed aircon and whether they regret it?

exactly what it says .. insulation in roof space is specified by building regs. We have a large dormer and there is a lot of cellotex plus superfoil insulation which works to keep warmth inside in the winter and keeps the room cool in summer. Ventilation - windows front and rear for a cross flow.

I have air con in my loft conversion. Love it. Space gets v. Hot so we need air-conditioned to make it use able in the summer.

There does need to be ventilation in the roof too though
is eaves, ridge, between the roof insulation and the membrane

I'm sleeping in a loft conversion in the south of England now and it's fine, no Aircon needed. No roof lights though.

We're about to get ours done and DH is very very against getting Aircon. He thinks we would need it max 4 weeks a year and we could use a portable one for that. It's a full mansard though so won't have a roof light and generally the house is cool. I'm retaining the option to get it done- but it might depend on your personal tolerance as well. Both DH and I have lived in very hot countries and hate sleeping in Aircon. It can be useful to cool the room for 20 minutes before bed but I'd almost always turn it off before sleep.

The hottest room in our house currently is the one with zero insulation and single skin brick, so the insulation has to help!

Yes get aircon for a loft conversion - you've removed your insulating layer so you need something to help.

No to dormer windows. We have one in DD's room and it is the worst thing - the ceiling slopes either side of the window such that the wall height is about 3ft at that end. It seriously limits the furniture we can use, and is only attractive from the outside. If it's the only option try to get the window beside a wall, so the slope is only one side. If I had the money I'd love to redesign our house to get rid of the stupid dormer.

Modern insulation standards are designed to both keep heat both in and out, but other factors are influencing such as the orientation and solar gain from the roof and glazing.

If the roof is south or west facing, the loft will be likely to overheat. A loft room without good airflow from cross ventilation can trap heat.
Also if the windows are roof lights as opposed to vertical ones in dormers, the solar gain increases. I’d think about these factors before making a decision.

Yes, I would, also the fitted in ones are quieter and cheaper to run. We have a couple of the mobile ones and they are very noisy and similar sort of price to an oil filled radiator to run.

We did this in our old house and worth every penny. And that was after we had insulated the wazoo out of the loft anyway. You’ll find that when it’s really hot the entire household migrates to the loft.

One point to make- ours makes far more economic sense as we have solar panels to (partly) power them. Otherwise rather expensive to run albeit we don’t expect it will be terribly often. At least not yet.

Yes. I wish we had.

@Aleiha I'm interested in that idea. we are also on oil. I didn't know you could get a single room ASHP? That might solve some other problems for us.

@PigletJohn thanks for explaining that.
Our house was a barn conversion 40 years ago. It does have some slabs fixed inside the roof timbers, no idea what the composition is.
Because it's basically cottage style the ceilings are very low and sloping. My ideal would be ceiling fans but you couldn't do it in this house.

We live in the north and the bedrooms are hot any time in summer on a sunny day, but on days where the outside temp is high 20s or above it's unbearable.
In recent years that's been probaly two or three weeks in total per year.

My best purchase ever was a portable air con unit. In a couple of hours it can get the room temperature down from furnace to fridge. It certainly eats electricity but then on those days our solar panels are running it.

Definitely worth it

Can you share what portable aircon unit you have? We cope pretty well with heat usually, but something to take the edge off in the afternoons would be amazing.

Yes I would.

yes to that

we had to replace our roof and took the opportunity for extra insulation. we also changed the windows to triple glazing and painted the dormers white.

no need for an aircon. the upper story stays at a pleasant temperature all year round.

@hairstreak it's this one. No longer available but you can see the idea.
https://www.amazon.co.uk/dp/B01GJONCMS?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1

I bought it in a January sale donkeys years ago. It's been fabulous and is very powerful without being too noisy. It's on wheels which is handy because they are heavy. I just wheel it into a spare room to store over winter.
DS2 recently moved into his own house and one of his first purchases was a portable air con. He doesn't even have loft bedrooms.

Thank you!

Air to air heat pump so it heats and cools. Run off solar panels if possible to install when doing the loft. Get the solar awnings for any velux rooflights.

We didn’t but I wish we had as it gets incredibly hot in the summer. We never have radiator on up there in the winter.

We have air con in loft conversion, wouldn’t be able to sleep up there in the summer without it. We also have solar panels and a Tesla battery so barely costs anything to run in the summer.

We have aircon in our South facing bedroom. It was 30° in there this afternoon even with the curtains closed. No way I could sleep in that temperature! We've had it probably 10 years now and apart from the water softener it's the best money we've spent. I'd highly recommend installing it (ours heats too.)

We have 2 bedrooms in dormers. Hot as hell so luckily yes we do have AC.
If you can afford to put it in why wouldn't you ?
Better for resale too.
X

We are in the process of applying for planning permission to put a dormer into the bedroom on our second floor. We’ve assumed that air conditioning is a must. Our second floor is really cold in winter (we use a standalone heater in there as well as the normal radiators) and really hot in summer so installing air con as part of the build is a must for us. We’re in the south east.

South of England, Surrey area.
Attaching the temperature charts for our loft conversion bedroom for yesterday and today. We’ve got two velux windows on the east facing side and dormer windows on the west facing side. Blackout blinds and external anti heat blinds on the velux windows and blackout curtains on the dormer windows. Loft conversion is done properly with all the right insulation, just about 5 years ago.

If we have the windows open when it’s 30 degrees outside it will be at least 30 degrees inside so we keep them closed with curtains etc closed till the sun gets low, then go up and open it all up and put the fan on. But it’s still very warm at night when it’s 30+ temps like this, and far too hot during the day. It takes ages to cool down too. Been experimenting with all sorts of windows / curtains open/shut at different times of day over the years and none of it stops the room getting up to over 30 when it’s hot out like this.

I wish we’d put air con in - it’s really only about 3 weeks per year that this is a problem, so we’re ok really, but it would be great for it not to be so hot and make the room unusable during the day. At night we can just about manage with a floor standing fan going.

Yes and allow for it as part of the conversion but have it installed separately - that way you can have the a/c installation at the current 0% VAT rate rather than paying 20% as you will be for the other materials (and probably labour). If the a/c is part of a bigger project i.e. the conversion, it is 20% VAT, if the a/c is the main project then until spring 2027 it's 0% VAT.