Insulation/ heat loss advice

[Yoda21]

Looking for some advice on where to start with our freezing extension🥶Our main house is a 1900 house and a large extension was built on about 15 years ago. The extension is an open plan kitchen/living and has a utility and bathroom off it. There are large sliding window doors on two walls and a large lantern skylight with a flat roof. It seems one of the sliding doors lets a huge draught in but must be something else too. We got the internal walls pumped last year and it has made no difference. We’re not sure who we would even ask as what needs to be done - is it a thermal imaging 🤷🏻‍♀️or insulation expert?? The floors are very cold tiles and there’s large radiators as heat source. Thank you.

The next frosty morning get someone up on a ladder to check if the flat roof is frosty or if it’s clear due to heat loss. It may not have adequate insulation.
Our dining room is cold unless we close the heavy curtains over the sliding doors. We don’t even have any draughts, they are only 4 years old, but the heat loss because of the cold glass is quite noticeable. Have you got curtains up?
Maybe think about large rugs for the floor, or changing it for wooden floors? DF was in a house with old quarry tiles on the whole ground floor and it was permanently freezing. Putting carpet down in the living room made a huge difference to that room.

Get rid of the lantern roof light. If possible replace the glazing units in the double glazing. External insulation.

Get an Energy Performace Certificate and it will let you know what improvements can be made.
Pumping into the cavity wall may have made the situation worse.

No it won't. It will just tell you how much loft insulation you have, whether they assume your walls and floors are insulated and tell you to install solar panels.

It won't actually tell you how to make a room warmer.

You can get energy efficiency experts but I don't think you need one. Most of the heat will be going out of the flat roof, they are exceptionally bad for heat loss. Even if they are insulated, it can only ever be about 1/3rd of the amount of a normal roof. You might be able to counter some of it by applying thermal wallpaper to your ceiling, or maybe even thermal boards, although obviously you will lose some height. Next is glass: windows, glass doors, sky lantern. For the glass doors you can get a thick, thermal lined curtain. You can check for draughts by lighting a Joss stick when it's a bit windy and watching the smoke move; fill in any gaps.

I have no idea how to deal with heat loss through a sky lantern, but I suspect when you deal with those other two issues, it will matter far less.

Finally, flooring. Porcelain tiles will be a lot colder than lino. If you have a kitchen diner, can you put a massive rug in the dining area? At least your feet will get less cold when eating.

Having two other cold rooms (WC, utility) will also make that space colder; if you are prone to keeping radiators off in those rooms, try keeping them on. My kitchen is absolutely balls off if I have the door open that leads to those two rooms. Consider draught excluders on the bottom of the doors of those two rooms too.

Just to add, even a pitched roof extension will be colder than the normal parts of the house, because they usually have three exposed sides, whereas much of the rest of the house will have one or two.

Thermal lining paper is something you could add to the walls as well, come to think about it.

I recommend thermal paint. it goes on thick but the end result is brilliant. easy to paint over too (we painted over with Dulux)

we used it in an uninsulated extension and it's transformed the entire room and house. humidity has reduced, no more condensation and it's now a usable room.

https://www.amazon.co.uk/Rempro-Thermal-Paint-Litre-Condensation/dp/B07B677LG6/ hope the link works!

Oops I forgot to say the whole house is warmer. we only painted 2 exterior walls 😊 the walls are warm to touch

Many thanks for all the helpful advice 🙏🏻I think we need to get thermal curtains , look at changing the floors and see about putting boards up on the ceiling. Will look into thermal paper / paint too. Really appreciate the steer as we haven’t a clue and don’t want to fork out for more work that won’t make a difference.

Correct.

EPC’s are not fit for purpose.

Thermal paint has got to be a joke hasn't it?

Otherwise why spend thousands and give up 100mm of space when you can just slap on a few coats of paint?

Definitely defies the Laws of physics

We had a flat roofed extension, a bit older than yours though, 1970s. Insulated at some point when it was redone pre-us within the last 16 years or so, but only with fibre glass between the rafters, which is probably what you have???. Modern 'warm roof' flat roofs are much warmer. We also had 2 pretty old double patio doors, which we replaced, it made some difference, but not masses. Where is the draught coming from on yours? If it's round the edges, could you seal it? Or is it just the cold downdraught from the glass? If it's that, well, we inherited full-length lined velvet curtains over the doors when we came here, and though they are rather worn and venerable at this point, the do help a lot in terms of warmth.

We put a pitched roof on ours a year ago and joined it up the the main roof (which is 1-storey just there). Building regs had us put masses of PIR insulation in the new roof, and though the roof is much higher, it's warmer in there than it was, even with skylights which it didn't have before. What I do notice is that even with all the insulation and with modern veluxes, it is still warmer at night if we close the blinds on the veluxes. I wonder how much heat you're losing through the lantern?