Old house? Cold feet? Find out how to insulate under a suspended floor

If you live in a house built before 1930 you’ll have a suspended floor. And you’ll probably be cold! Up to 20% of heat goes out through the floor but it often feels like more than that.
You can easily insulate between the top of the air brick and the floor boards. Best way is with flexible, sustainable insulation held in an airtight breathable membrane.
Take a look and let me know if you have questions.
Materials mentioned:
1. Wood fibre insulation - different types available. This one is Pavaflex. unitylime.co.u...
2. Contega tape: www.ecological...
3. Airtightness membrane: unitylime.co.u...
4.. The official version of way of insulating under a suspended floor: www.ecological...
#energysavings #retrofit #tedxtalks

[@pumpkinhead456]

Well done John, and well explained. I figured out the same system 2 years ago. I tried initially without the breather membrane but it was drafty!

[@ecorenovationhome]

Well done sorting it out! The architect who supported me writing the book made very clear that insulation without airtightness would be disappointing. Draughts get through the merest slither. Did you redo it?

[@zzaman2141]

Thank you Judith, a great breakdown!

[@ecorenovationhome]

Thank you so much. Glad it all makes sense!

[@pepols1510]

We have been looking into doing ours as we want under floor heating would your method work the same as I was thinking we have to baton and kingspan it?
Great demo 👌🏻

[@ecorenovationhome]

Underfloor heating is fine over insulation. Kingspan is not your best option. Suspended floors move and it won't move with it, so you'll end up with draughts coming through. Plus it uses toxic chemicals so not good for health in a well insulated airtight home.
We discovered a product called Econna Board which went on top of the joists/ insulation. It is tongue and groove which means better for airtightness and it has grooves for the UFH pipes. No idea about the providers here, but this link will give you an idea of what I mean. www.warmup.co.uk/underfloor-heating/water/econna-joisted-floor
Hope that helps. Let me know if you have more questions. You can read more about it in my book if that would be of any help amzn.to/3EOBHjM It's a lay persons summary of the whole retrofit process, so you have enough of the basics to talk sensibly with the builders (who don't know a lot more than we do!)

[@user-ei2zg6mi1c]

Never knew about the wood insulation!! Can this system be used in a suspended floor on a 1980s build do you think?

[@ecorenovationhome]

Well there you go - I didn’t know you would have a suspended floor in an 80’s house! We’re all learning🤣🤣.
There are so many different firms if insulation now. It amazes me. Wood fibre is just one of the sustainable options. Just take a look on this site to see what’s possible
unitylime.co.uk/product-category/insulation/
This site shows the formal way of doing what we did ourselves and talks about reasons for different types of insulation. Let me know what you think.
www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

[@matthewdeakin8266]

Hi - please can I check. The membranes used to sit the insulation in and top off under any floor are both breathable?

[@ecorenovationhome]

Hi Matthew - yes, the same membrane is used for both. It's a breathable, airtight membrane. It will usually need to be breathable since it is primarily houses built before 1930 that have suspended floors and they were all built as breathable systems. Hope that answers?

[@matthewdeakin8266]

It does thank you, I’ve seen other systems where the bottom is airtight and breathable but the top is not breathable. The reason given is to prevent moisture condensing. To me that doesn’t make sense as you’d trap in moisture and the underfloor vents should take care of any moisture. This approach seems to make more sense.

[@ecorenovationhome]

@@matthewdeakin8266 Totally agree with you. That makes no sense. Full breathability is what will stop moisture condensing.

[@fahd.m8669]

I’ve installed spray foam insulation, what are your thoughts on that?

[@ecorenovationhome]

I think it works well but there are concerns. Not so good for the environment. Need to make sure your insurance covers it. Some mortgages lenders don’t like it - so worth remembering that if you’re going to sell. How is it working?

[@kingquinn3897]

Is there any brickwork under the floor...I mean to hold the joists?

[@ecorenovationhome]

Hiya - the joists go into the brickwork of the walls and there is a small brick wall across the middle of the room to support the joists.

[@kingquinn3897]

@@ecorenovationhome Is there a chance that damp could rise up the bricks and into the timber?

[@ecorenovationhome]

@@kingquinn3897 Yes. To avoid that the joists sit above the damp proof course, so it blocks any rising moisture and above the air bricks to stop condensation.

[@kingquinn3897]

@@ecorenovationhome Thanks for that. But was the damp proof put in all existing buildings when they were built or is this something that has to be added now?

[@ecorenovationhome]

@@kingquinn3897 my understanding is that a DPC was out into older houses. Often layers of slate. I know we had that (1901) We also had an injected DPC added.