Insulating Suspended Wooden Floor or not advice needed!

dublinbay34

Hi All,

I have gone down a rabbit hole of insulation and gotten lost and need some advice!

I have purchased a 1950's Semi-D BER Rating F. The rating is a little surprising as the house is in liveable condition, and has a new gas boiler (<5 years). We are doing mostly cosmetic renovations before moving in and considering any major works. These works involve replacing the carpet in the hall and 2 reception rooms with either a laminate or engineered wood floor.

My issue is the level of insulation that I should put in now as I am cognizant that once an engineered floor goes down it can't be lifted without damage. I have lifted the carpets and taken the skirting off and as expected there are a lot of draughts between the meeting of the walls.

My plan was to lay a small piece of plastic sheet between the floor and wall then lay the floor on top and place the skirting over and caulk which should block drafts coming from the skirting.

However I am wondering should I go to the effort of lifting all the floorboards and put in insulation between the joists? How much benefit it would give? The existing floor is in good condition and if I lay a tongue n groove engineered floor over it should be insulated enough? I wouldn't be able to do the lifting of the floorboards myself due to time so any idea of companies that do the full service and costs involved?

Lastly, if I am not undertaken works now to insulate should I just lay a laminate with a good underlay on top of the floor?

I also have a slight concern about laying a thick engineered floor ontop of the existing floor creating issues with levels into rooms that do not have the floor installed and doors etc.

Any advice/experience much appreciated

Calahonda52

https://www.ecologicalbuildingsystems.com/post/best-practice-approach-insulating-suspended-timber-floors

do it once and right

https://www.nsai.ie/about/news/publication-of-sr-542014-code-of-practice

WildCardDoW

I had the same issue. I eventually went with the below:

Spray foam suspended on breathable vent cards, all supplied by the spray foam company. We also underlined the joists with the rigid boards at the recommendation of the SEAI Technical Advisor who said the spray foam will be a good choice (mentioning that to pre empt the doubters on it).

It probably isn't as good as doing the same with actual rigid insulation as per the link from ecological above.

Then you should buy the sealing tape or foam and complete your current plan:

https://www.mcmahons.ie/siga-rissan-100-adhesive-tape-100mm-x-25m-green

If you can do it you could also insulate the external facing walls or otherwise check if external or internal insulation is best for your house.

I'd assume it's solid block so I think an external wrap down the line should be good.

dublinbay34

WildCardDoW wrote: »

I had the same issue. I eventually went with the below:

Spray foam suspended on breathable vent cards, all supplied by the spray foam company. We also underlined the joists with the rigid boards at the recommendation of the SEAI Technical Advisor who said the spray foam will be a good choice (mentioning that to pre empt the doubters on it).

It probably isn't as good as doing the same with actual rigid insulation as per the link from ecological above.

Then you should buy the sealing tape or foam and complete your current plan:



If you can do it you could also insulate the external facing walls or otherwise check if external or internal insulation is best for your house.

I'd assume it's solid block so I think an external wrap down the line should be good.

Thank you, I assume you had to lift all the floorboards to do the spray foam? I am struggling to find an insulating contractor in Dublin who will also lift and replace floorboards.

When you say complete my current plan with the tape, do you mean use is to tape the small plastic sheet to the wall and the floor?

dublinbay34

Calahonda52 wrote: »

do it once and right

Thanks, I am struggling to find anycontractors that would do this in Dublin including removing and reinstalling the floors.

Calahonda52

even harder to get someone who
a: understand the task
b: will execute according to plan and do it right

dublinbay34

Calahonda52 wrote: »

even harder to get someone who
a: understand the task
b: will execute according to plan and do it right

Thanks for the links above that NSAI document is very useful. The eco homes looks a little complex to execute. I am seeing the benefit in doing it now, and taking the time to get it done.

I think roughly probably what I will do is lift the floors myself, get somebody in with experience to do the insulation involving a material between the joist plus a membrane above the top and relay the floors then put a laminate on top to keep the costs down.

WildCardDoW

dublinbay34 wrote: »

Thanks for the links above that NSAI document is very useful. The eco homes looks a little complex to execute. I am seeing the benefit in doing it now, and taking the time to get it done.

I think roughly probably what I will do is lift the floors myself, get somebody in with experience to do the insulation involving a material between the joist plus a membrane above the top and relay the floors then put a laminate on top to keep the costs down.

Yes, you'd need someone to lift the boards you could look at putting 18mm OSB down after and see if someone will do that if you do the lifting!

The general advice is a layer below the insulation (that's what the cards do in the system I had) and then another layer above. The layer above should be acting as the airtightness layer and the layer below should be a breathable membrane.

With the OSB you'd get away with your plan, with floorboards you would need to go over the full floor. That's just my opinion though so check with an expert if you are concerned.

mloc123

I would consider cost versus return... in an F rated house, I think wall and roof insulation along with new glazing will have a much better return

Calahonda52

mloc123 wrote: »

I would consider cost versus return... in an F rated house, I think wall and roof insulation along with new glazing will have a much better return

Not unless the floors are are least airtight

Pete_Cavan

Would you consider cutting out the joists and putting in a proper floor slab with insulation, radon barrier, etc? Could even have under floor heating.

listermint

mloc123 wrote: »

I would consider cost versus return... in an F rated house, I think wall and roof insulation along with new glazing will have a much better return

BER sucks as a system. Incremental changes like the OP is doing massively make a difference to comfort levels.


I'd take comfort levels over arbitrary numbers on a spreadsheet any day.

dublinbay34

WildCardDoW wrote: »

Yes, you'd need someone to lift the boards you could look at putting 18mm OSB down after and see if someone will do that if you do the lifting!

The general advice is a layer below the insulation (that's what the cards do in the system I had) and then another layer above. The layer above should be acting as the airtightness layer and the layer below should be a breathable membrane.

With the OSB you'd get away with your plan, with floorboards you would need to go over the full floor. That's just my opinion though so check with an expert if you are concerned.

I have seen the bottom layer as netting with soft material on top or the kingspan rigid boards.

I think relaying the floorboards plus an underlay and the laminate should be very good as for some of the floors I am considering just using the original floor boards!

karlitob

listermint wrote: »

BER sucks as a system. Incremental changes like the OP is doing massively make a difference to comfort levels.


I'd take comfort levels over arbitrary numbers on a spreadsheet any day.

I’ve a similar set up as OP. Our builders put in foil backed insulation between the joists when we renovated 10 years ago, I presume OSB on top of that. I didn’t think at the time it was a great job and I’m not sure how good they were and putting it right up to exterior walls. Certainly no tape at the edges of the room.

I’ve notions of updating the insulation when I redo the carpet. But just wondering if there’s any point. Is a lot of money and effort for very little return?