UFH in bungalow

V2001

im building a extension which will tie in with my existing bungalow.  ufh is to run throughout.

can i do the following:
1. lay pir boards like cellotex floating 100m in the new extensions, and then 20mm in the old part of the house.  this makes all the floor level one height throughout.
2. lay overylay ufh boards 22mm floating over the cellotex
3. then lay on top of the ufh boards a underlay, then engineered oak flooring (all floating)

would this work?

FreeBear

V2001 said:

im building a extension which will tie in with my existing bungalow.  ufh is to run throughout.

can i do the following:
1. lay pir boards like cellotex floating 100m in the new extensions, and then 20mm in the old part of the house.  this makes all the floor level one height throughout.

You would be much better off taking up the entire floor to put a decent amount of insulation down (I'd suggest 150mm). The heat loss through 25mm of Celotex (don't think you can get 20mm) is going to be comparatively high and will increase your running costs.

V2001

FreeBear said:

V2001 said:

im building a extension which will tie in with my existing bungalow.  ufh is to run throughout.

can i do the following:
1. lay pir boards like cellotex floating 100m in the new extensions, and then 20mm in the old part of the house.  this makes all the floor level one height throughout.

You would be much better off taking up the entire floor to put a decent amount of insulation down (I'd suggest 150mm). The heat loss through 25mm of Celotex (don't think you can get 20mm) is going to be comparatively high and will increase your running costs.

Will this heat loss occur even with using overlay boards for ufh that are insulated 

Doozergirl

You're going ti get movement if you attempt to lay over floating insulation. 

also, what is the insulation like in the walls/roof of the existing building? It needs to be good or you won't be able to maintain the temperature in the house.  Historically, I've always guided people away from UFH unless effort is being made to improve overall insulation as well to match the extension.  

onomatopoeia99

FreeBear said:

V2001 said:

im building a extension which will tie in with my existing bungalow.  ufh is to run throughout.

can i do the following:
1. lay pir boards like cellotex floating 100m in the new extensions, and then 20mm in the old part of the house.  this makes all the floor level one height throughout.

You would be much better off taking up the entire floor to put a decent amount of insulation down (I'd suggest 150mm). The heat loss through 25mm of Celotex (don't think you can get 20mm) is going to be comparatively high and will increase your running costs.

Taking up the existing slab is going to be massive disruption, cost and mess though, which are significant factors to consider and why retrofit systems are popular when installing UFH.  The savings on heating bills from digging out the slab and relaying it with insulation are unlikely to ever repay the cost of the work, unlike with loft or cavity wall insulation, which if properly done does pay for itself in a relatively short time period.

Doozergirl

But your wallls only have a v small cavity, so no insulation.  Unless you're going to retrofit internally/externally?