Hi all, looking for the insulation experts.

My house was built in 91 so insulation isn’t great. My kitchen/living has 3 exposed walls and really struggles to hold the heat. Adding insulation to the walls isn’t really an option at the minute as I don’t want to tear down the plasterboard. I have wooden suspended floors and wondered if insulating the floor is worth it? Will it make a noticeable difference to comfort and bills?

Thanks for help in advance. 🙂

The right order is roof/ceiling, walls then floor.

What do you know about the construction?

This is my current project – suspended floor with airbricks, 2-3ft gap underneath. You can feel the temperature difference at ground level even with carpet and underlay.

My suspicion is that it won’t make a huge difference to bills, but quite a bit to comfort. My wife likes to lie on the floor! I’m only doing it because the walls and loft are already done.

it depends. how drafty is your house. mine is really cold on windy days. most of it comes via the exposed floorboards in the hall.

you can get those thermal cameras relatively cheap and have a look to see where you are losing the most heat

Saw a firm last week who drive a remote controlled car with a spray gun and camera on around underneath the floor spraying foam insulation under the floorboards. No idea if it works well.

Saw a firm last week who drive a remote controlled car with a spray gun and camera on around underneath the floor spraying foam insulation under the floorboards. No idea if it works well.

I’d be worried about how breathable that is and what happens to moisture that ends up on or under the floor. The whole point of these underfloor spaces is that they’re ventilated. Given the room is part living room a washing machine leak or whaterver would leave any water that gets into the floor – ie between the floorboards and joists – nowhere to go.

RNP’s contribution to this thread https://singletrackworld.com/forum/topic/spray-foam-roof-insulation-2/ makes interesting reading in relation to spray foam.

I’ve just this morning ordered up materials to do the floor in the living room of the house I’m moving into. Have the luxury of an empty building for a few weeks before we move in so just going to lift the boards and do the job property rather than bork myself trying to wriggle aroind in a rubble strewn crawl space.

We’re going for mineral wool slabs sandwiched between two breathable membranes – more or less like this https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

I did, yes it made a difference.

Rockwool between joists held up with bird netting. PITA installing (I had the boards up anyway as it was a complete replacement) but once done and edges sealed the comfort levels improved dramatically.

If I was doing it again then I’d absolutely follow that link above! I also found that the cost of replacing a few boards (we had a wall knocked down and had some others needing sorted) was the same as resheeting the entire ground floor in 18mm damp proof chipboard. Chipboard it was, no issues with creaks as it was all properly pilot drilled and joints sealed with PVA.

I’ve done it in our house, and it does make a difference. Helpfully we have proper cellars, so I was able to do 3″ Celotex fairly easily. (still a messy job, but at least I could stand up!)

If I only had crawl space access, It would probably have to be rockwool in netting, but it would be a disgusting job to do! Would almost consider ripping the entire floor up, just for ease of access.

I’ve insulated all the suspended floors over the last eighteen months, difference is noticeable immediately, mostly comfort rather than reduced bills but it is well worth it.

100mm loft insulation and a breathable membrane stapled across the bottom of the beams. I used membrane rather than netting as I’d read that on windy days the high airflow under the house can wick the heat away, how true this is I don’t know but I was only going under the floors once 😀

Done two houses. Once crawling about under to fit rock wool with wire netting. Horrible horrible job. Once lifting up all the floors and replacing, which we got someone else to do, and we did it that way in part to work as a package with fitting underfloor heating. Both made a pretty big difference in my view, but I can’t prove it. Roof then walls then floor in order of importance but it might be that your floor is the bit that falls furthest short of current regs/practice, in which case it might go top of the list in your circumstances. Moisture/breathing is an important consideration whether working on floor, walls or roof.

Thanks for all the replies. So yeah roof- done. Walls – I think it’s just shiny bubble wrap. Did this used to get used rather than wool? Had a crawl under the floor today. Can get under every room except one half of the kitchen/living room. Probably no point in doing half the room is there?

Any sensible way to insulate a wooden floor on top of the floor rather than underneath as a tenant?

We’re in a rented house and our two bedrooms have a a timber floor over a void with external wall vents into it. I can’t see the landlord lifting the floor to insulate, but i might be tempted to lift the carpets myself and put some sort of space blanket type stuff down under it. Any underlay if exists will be pretty crap, so maybe there’s a ‘super’ underlay we could get?

Last winter it was so cold and drafty depending on the wind that I loosely blocked off/shielded the the air vents with planters infront of them and it did make a difference. I’m tempted to properly block them off over this winter.

Cloud 9 underlay, the 11mm thick stuff, about as good as it gets and will certainly make a difference, it did in our old house.

I blocked off my air vents with expanding foam as the housing association refused to insulate the suspended floor due to no money available and if they did my house then they’d have to do every house (their exact excuse), still get plenty of draughts throughout the house and from the floor due to piss poor construction (the local firm who built my house in the late 80s went bust due to being taken to court for not following building regs)

Cheers Flicker will check it out 👍

There wasn’t enough space to move around so I dug trenches under the house. The ground is quite hard and stoney so that took some time. The insulation is 120mm recycled polysester which is much nicer to work with than rockwool etc. I wanted it to fit well to reduce draughts through the wooden floor so it took some time.

The result is a floor which is about R3: R .3 for the floor boards + R 1.2 for the solives and R 3.2 for the insulation.

In terms of comfort it’s nice not needing to wear shoes or socks. I’m currently typing barefoot at 21°C. We don’t have any central heating but burn a couple of m2 of wood over a Winter.

The house isn’t perfect R 3 floor, R2.5 – R4 walls and R6 – R8 roof. The extension I’m building will have better insulated walls. The objectives have evolved, to get into category A+ walls have to be >R5 these days.

Digging trenches…that’s impressive! Well done!

Ex-caver 😉

Ex-cavator