ATW Heat pumps? Help!

Zax

Hi all,
Hoping for some help with this please. Building under the new regs and considering a heat pump with underfloor heating. Have been told that if I want oil, I need to install 6-8 sq metres according to the preliminary BER. There isn't an option for a south-facing roof, only an east-west configuration.

The house is 2,500 sq feet and 1.5 storey.

Insulation will be;
100mm xtratherm in the cavity
100mm insulation in the floor
68mm insulated slabs on the ext walls
300mm insulation in the attic

Taking this into account, it's looking like a heat pump will be the way forward. Really want to hear from someone with an ATW system already installed. Particularly want info on running and installation costs.

Thanks! #confused!

dathi

if you are going with an air to water heat pump you should have underfloor heating to maximize the COP of the heat pump, and if so 100mm is not enough insulation in your floor. also most people recommend putting all the insulation in the cavity and not using insulated plasterboard . this helps by having the blockwork acting as a thermal mass it helps even out the highs and lows of demand, also there are problems using insulated plasterboard with regard to detailing air tightness and condensation . also as your house is dormer you will not be able to have a continious layer of 300mm insulation what details have you for the stub walls and the sloping ceiling and most important what are your air tightness details for this area.

MicktheMan

Zax wrote: »

Hi all,
Hoping for some help with this please. Building under the new regs and considering a heat pump with underfloor heating. Have been told that if I want oil, I need to install 6-8 sq metres according to the preliminary BER. There isn't an option for a south-facing roof, only an east-west configuration.

The house is 2,500 sq feet and 1.5 storey.

Insulation will be;
100mm xtratherm in the cavity
100mm insulation in the floor
68mm insulated slabs on the ext walls
300mm insulation in the attic

Taking this into account, it's looking like a heat pump will be the way forward. Really want to hear from someone with an ATW system already installed. Particularly want info on running and installation costs.

Thanks! #confused!

Who drew up those specs!
In this day and age, splitting your wall insulation between the cavity and internal is madness. Also, I wouldn't advise installing insulation boards in the cavity...pump it instead.
Double your floor insulation.
You don't mention airtightness ... in a 1.5 storey / dormer house this is more important than insulation!

Imo, you should forget your heating questions for the moment and concentrate on getting your building envelope / fabric right first. It then gets very easy to supply the required heating.

Zax

dathi wrote: »

if you are going with an air to water heat pump you should have underfloor heating to maximize the COP of the heat pump, and if so 100mm is not enough insulation in your floor. also most people recommend putting all the insulation in the cavity and not using insulated plasterboard . this helps by having the blockwork acting as a thermal mass it helps even out the highs and lows of demand, also there are problems using insulated plasterboard with regard to detailing air tightness and condensation . also as your house is dormer you will not be able to have a continious layer of 300mm insulation what details have you for the stub walls and the sloping ceiling and most important what are your air tightness details for this area.

Thanks Dathi,
I should have stated that the specs are for oil so obviously will need to be changed to suit underfloor. Floor insulation will def need to be increased... Really at this point looking for info on the ATW system as need to decide on heating before fit the insulation to suit (then can decide on any other changes to insulation) any experiences of the ATW?

Borzoi

Zax wrote: »

Really at this point looking for info on the ATW system as need to decide on heating before fit the insulation to suit (then can decide on any other changes to insulation) any experiences of the ATW?

Weve had ours since 2010. House is new 2 storey 3000sqft and a3 rated. ATW with underfloor everywhere. Heating cost is probably €1500 pa. We could reduce that by going to night rate but Mrs B is very sensitive to plumbing and pump noises at night.
Good points
house temp is very stable
poor points
system can be slow to react to extreme changes in outside weather.

plenty of other threads about ATW elsewhere. If we were building again I'd do the same thing ( or if mains gas was available it would be down to the wire)

kscobie

I priced a new house last week, and there was a condensing oil boiler on the spec, along with 6sqm of solar and a wood burning stove.
Once the insulation and air tightness is good enough, and obviously, this is done at the design stage, your options are increased.