Floor - insulation between joists.

BryanF

BoardsMember wrote: »

Noted. We'll be using the services of an architect for the renovation/extension. Is this something that would allay the concerns, assuming our builder is a reliable sort? i.e. does that bring back onto the table the extra cost.

If you have the time....you mention needing thermal mass, and say not dry lining. It's a part red brick, so external insulation is not an option except on the new extension and back of the house. Is the issue with dry lined that the walls are not acting as thermal mass, or are there bigger issues?

Not necessarily. You need a site assessment

fmlarnapairce

bumpity bump

BryanF

BryanF wrote: »

1920’s house? don’t do it. Unless the place is really well insulated/thermal bridges addressed, and has thermal mass (ie not dry-lined)

BryanF wrote: »

Down to the detailing and supervision - most people can’t stomach paying for design/detailing & site supervision - assuming this don’t bother installing ufh

fmlarnapairce wrote: »

bumpity bump

.

BoardsMember

If that is directed at me....

Yes, 1920s house. I've already had a thermal survey done so I know where improvements need to be made

The renovation will be done under the direction of an architect who has good knowledge of insulation considerations, so I am happy that the design and detailing will be appropriate.

I'll probably engage an expert third party to do a site visit to get their thoughts on insulate versus back fill, underfloor, thermal mass considerations, ventillation, dry line everywhere versus partial ewi (red brick to front so can't to that competely).

fmlarnapairce

hi, nope not directed specifically at you but at anyone who can advise, but thanks for above, i had not considered getting a third party expert in to see what should be done, i will do that. all the best

caesarthechimp

Sprayfoam between the floor joists will take care of insulation and draughtproofing, and also stiffen and strengthen up the floor if its a bit creaky. Deals with everything except the rats underneath.


Mind you, a basic uninsulated suspended floor can sometimes be an advantage because its relatively cheap to rip out if you were looking at installing a really well insulated concrete floor with underfloor heating combined with an air source heat pump. Taking out a crappy concrete floor and then excavating the hardcore to get enough extra depth for the insulation is a builders nightmare.

fmlarnapairce

caesarthechimp wrote: »

Sprayfoam between the floor joists will take care of insulation and draughtproofing, and also stiffen and strengthen up the floor if its a bit creaky. Deals with everything except the rats underneath.


Mind you, a basic uninsulated suspended floor can sometimes be an advantage because its relatively cheap to rip out if you were looking at installing a really well insulated concrete floor with underfloor heating combined with an air source heat pump. Taking out a crappy concrete floor and then excavating the hardcore to get enough extra depth for the insulation is a builders nightmare.

thanks, yes this is the decision we have been trying to make for months. our problem is that while the air source and new floor would be a no brainer if the house was 1 story, the installation of UFH in the second floor is the issue. Seems mixing ufh and rads on the one air source HP is not ideal due to the different optimal temps for ufh and rads. that is why we're leaning towards just going with rads and oil all over, system is in place and working fine. insulation in the house is brutal though as was built in 1932

GreeBo

fmlarnapairce wrote: »

thanks, yes this is the decision we have been trying to make for months. our problem is that while the air source and new floor would be a no brainer if the house was 1 story, the installation of UFH in the second floor is the issue. Seems mixing ufh and rads on the one air source HP is not ideal due to the different optimal temps for ufh and rads. that is why we're leaning towards just going with rads and oil all over, system is in place and working fine. insulation in the house is brutal though as was built in 1932

Are you hoping to be boiler free or would you consider a smaller boiler just for upstairs rads?

dathi

fmlarnapairce wrote: »

thanks, yes this is the decision we have been trying to make for months. our problem is that while the air source and new floor would be a no brainer if the house was 1 story, the installation of UFH in the second floor is the issue.

google aluminium underfloor heating trays

fmlarnapairce

GreeBo wrote: »

Are you hoping to be boiler free or would you consider a smaller boiler just for upstairs rads?

hadn't considered this, i suppose we just want a simple one source system. but what you say could work.

fmlarnapairce

dathi wrote: »

google aluminium underfloor heating trays

this is interesting, you've put our build back a few weeks!

BoardsMember

Is it possible to get Air Source Heat Pump to do rads in any sort of an efficient/effective way? Thinking UFH downstairs, but rads upstairs, and not having to have to run a small boiler as well as the Air Source Heat Pump.

Would also be looking to use the heat pump to do the hot water, so maybe expecting too much of it. Planning to install Solar PV as part of a deep retrofit.

GreeBo

^
You can, but you will need to look at the BTU of your rads for the temps your HP will be giving them.

You will probably need to double the amount or size of the rads.

fmlarnapairce

It seems it is possible with aluminium rads upstairs but an extra buffer (I think) tank needed. I will know more shortly

Calahonda52

https://www.ecologicalbuildingshop.ie/news_detail.asp?newsId=7869
for ideas only

caomhino

Just wondering has anyone ever used PIR insulation boards between floor joists ?
I was considering using these in and sit them on batons and tape any gaps but reading in a few places that mineral wool might be a better option. Problem with the boards seems to be that they are rigid and inflexible. Any thoughts ?
Thx.

Polar wizard adventure

I used board and batons as you have described. I was able to do the work from the underside so didn't need to raise the floorboards (a good thing) but had to work in a crawlspace (a bad thing). You do need to be reasonable precise in the cutting of the PIR but any gaps on the edges or between the boards are pretty easily sealed with a good expanding foam gun. This also helps to ensure the boards stay in position. The downside with mineral wool is that it is air permeable so if there are gaps between the floor boards then it will only slow the drafts from below but wont stop them.

A lot of work but it worked like a charm.

BoardsMember

Polar wizard adventure wrote: »

I used board and batons as you have described. I was able to do the work from the underside so didn't need to raise the floorboards (a good thing) but had to work in a crawlspace (a bad thing). You do need to be reasonable precise in the cutting of the PIR but any gaps on the edges or between the boards are pretty easily sealed with a good expanding foam gun. This also helps to ensure the boards stay in position. The downside with mineral wool is that it is air permeable so if there are gaps between the floor boards then it will only slow the drafts from below but wont stop them.

A lot of work but it worked like a charm.

Presume you didn't use an airtight membrane so?

BryanF

Polar wizard adventure wrote: »

The downside with mineral wool is that it is air permeable so if there are gaps between the floor boards then it will only slow the drafts from below but wont stop them.

I’d rather have mineral wool & and vapor barrier on warm side, than timbers that can’t breathe due to PIR & foam.

Polar wizard adventure

Presume you didn't use an airtight membrane so?

No, the PIR and foam sealing is enough.

I’d rather have mineral wool & and vapor barrier on warm side, than timbers that can’t breathe due to PIR & foam.

The floorboards can breathe to the inside without issue. The joists can breath both to the inside and the outside.

My understanding of how a vapor barrier or airtight membrane would be installed properly is that it would require the floor boards to be lifted to get the full span of the floor.