So Heatpumps

[fred]

started first build last summer on new regs, no gas, 150 cav etc.

Had heatpumps fitted on several previous builds and they were costly to run, despite good levels of insulation and air tightness (so we thought).

As this is all we can fit very shortly decided to be meticulous on the shell, most of this is a labour cost rather than materials. We also (plumber) fitted the heat pump our self as i cant abide being bent over by some government scheme accredited con artist - MCS.

Fired it up last week to help dry out the plaster, loft is not insulated yet and has 44 downlight holes cut in it along with a loft hatch hole so certainly not airtight. Set the flow temp to 25c for underfloor to dry it all out gently.

results, downstairs a comfortable 16C, upstairs half that not surprisingly. Heat pump running at an average COP of 8 the last week.

COP meaning for every £1 of electric bought to spin the pump getting £8 of heating for free.

Solar hasnt been connected yet, very very surprised all the small improvements to the shell have paid off.

 

[DaveDCB]

Curious to know what changes you have made to the shell? Always keen to learn new build techniques

 

[fred]

quite a lot...

marmox blocks to delink internal walls from slab.
100mm ufh pipe spacing .
no zoning of UFH
150mm celotex on floor
thermally broken lintels
air tightness trays on pozi's
be anal on sealing every penetration through the walls.
air tightness caps (not fitted yet) to seal downlights in loft
windows fitted so only 20mm is projecting brickwork, majority is in the cavity and no trickle vents.
air tightness tape sealing windows to internal skin
high U value doors
MVHR unit so no holes through wall for showers, extractors, utility etc etc

sure there is more but thats off top of head

 

[Lancs Lad]

started first build last summer on new regs, no gas, 150 cav etc.

Had heatpumps fitted on several previous builds and they were costly to run, despite good levels of insulation and air tightness (so we thought).

As this is all we can fit very shortly decided to be meticulous on the shell, most of this is a labour cost rather than materials. We also (plumber) fitted the heat pump our self as i cant abide being bent over by some government scheme accredited con artist - MCS.

Fired it up last week to help dry out the plaster, loft is not insulated yet and has 44 downlight holes cut in it along with a loft hatch hole so certainly not airtight. Set the flow temp to 25c for underfloor to dry it all out gently.

results, downstairs a comfortable 16C, upstairs half that not surprisingly. Heat pump running at an average COP of 8 the last week.

COP meaning for every £1 of electric bought to spin the pump getting £8 of heating for free.

Solar hasnt been connected yet, very very surprised all the small improvements to the shell have paid off.

View attachment 58468

Interesting. Do you always use Panasonic?
Guessing they getting better all time? Surprising how little heat you can get away with on floor heating. Ours never above 21c

 

[Lancs Lad]

quite a lot...

marmox blocks to delink internal walls from slab.
100mm ufh pipe spacing .
no zoning of UFH
150mm celotex on floor
thermally broken lintels
air tightness trays on pozi's
be anal on sealing every penetration through the walls.
air tightness caps (not fitted yet) to seal downlights in loft
windows fitted so only 20mm is projecting brickwork, majority is in the cavity and no trickle vents.
air tightness tape sealing windows to internal skin
high U value doors
MVHR unit so no holes through wall for showers, extractors, utility etc etc

sure there is more but thats off top of head

Why no zoning on floor?

 

[JD450A]

From experience, heat pumps get hidden from view..... And then don't work....

 

[fred]

Why no zoning on floor?

it kills efficiency. heating up just part of a slab means all the surrounding area pulls heat from the heated part making the pump work harder. No problem with gas when its short on/off times very very bad for heatpumps which need to run constant and low.

 

[fred]

From experience, heat pumps get hidden from view..... And then don't work....

doesn't really matter where they go as long as they have the correct space around them, although closer to the cylinder for short pipe runs increases efficiency. mounted this one on first story wall other side of plant room so 750mm pipe run. they are whisper quiet when not driven hard as well.

 

[fred]

Interesting. Do you always use Panasonic?
Guessing they getting better all time? Surprising how little heat you can get away with on floor heating. Ours never above 21c

panasonic / valliant. Big Difference between slab temp and ambient temp. most gas runs 45C slab, to do same with heat pump costs £££££££££ hence low flow temp.

Retrofit heatpump without sorting the rest costs ££££ to run, can see why all the bad press.

 

[JD450A]

doesn't really matter where they go as long as they have the correct space around them,

View attachment 58471

That's the point.

A majority of them get boxed in or shoved in a alleyway with just enough clearance and then don't work properly.

Another winner is poorly insulated/incorrectly specified pipework that pisses heat out.... Especially when the customer has hidden it 10m away because it makes a noise.

 

[Lancs Lad]

panasonic / valliant. Big Difference between slab temp and ambient temp. most gas runs 45C slab, to do same with heat pump costs £££££££££ hence low flow temp.

Retrofit heatpump without sorting the rest costs ££££ to run, can see why all the bad press.

Yes...in our new build extension not so bad but old part needed triple monster rads and still struggles below 3-4c. If I was doing it again I'd either just have stuck to oil or done ufloor throughout now there's better board systems about.
Certainly not a direct replacement for oil boiler without other mods imo.
As it stands it'll have cost me zero on rhi plus I got a 305L tank and 75l buffer out of it as well so it's done us ok all said and done.

 

[fred]

Yes...in our new build extension not so bad but old part needed triple monster rads and still struggles below 3-4c. If I was doing it again I'd either just have stuck to oil or done ufloor throughout now there's better board systems about.
Certainly not a direct replacement for oil boiler without other mods imo.
As it stands it'll have cost me zero on rhi plus I got a 305L tank and 75l buffer out of it as well so it's done us ok all said and done.

all depends on your heatloss calcs, rads/fancoils can work well. I have fancoil units upstairs mainly for summer use when the heat pump can be reversed into cooling mode and cool the slab / bedrooms.

 

[Lancs Lad]

That's the point.

A majority of them get boxed in or shoved in a alleyway with just enough clearance and then don't work properly.

Another winner is poorly insulated/incorrectly specified pipework that pisses heat out.... Especially when the customer has hidden it 10m away because it makes a noise.

FFS make your mind up...last week you were an anti 4x4 tyre letter downer ...

 

[Regy53]

so we have just moved into our A rated for effiency house with airsource heatpumps and full underfloor heating.

its a learning curve so far but it isnt very efficent. or doesnt feel it, i need to understand some parts of our use but the old house was a average or 30kw a day i think, the other day at the new place it pulled 130kw, average about 80 kw a day so 50kw going on heat.

i think i have the temps set to cold and then wanting to get it to warm so going to change the thermostats today to work out

 

[fred]

so we have just moved into our A rated for effiency house with airsource heatpumps and full underfloor heating.

its a learning curve so far but it isnt very efficent. or doesnt feel it

interesting, is the UFH zoned ? good sign of the overall competency of the build.

You can pull the SAP calcs from planning to see exactly what the spec was.

 

[Regy53]

interesting, is the UFH zoned ? good sign of the overall competency of the build.

You can pull the SAP calcs from planning to see exactly what the spec was.

yeah every room is zoned and we have god knows how must insulation, tripple glazing etc.

i really dont know how to use it is my issue, currently i am letting it drop down to say 17 degrees which is to cold as we want it to 21 in the evenings.

im going to change it to minimum in each room of 19.5 and to peak at 21.5 during times at home.

 

[DaveDCB]

We have ufh downstairs and rads upstairs. Ufh is set to drop no lower than 17.5 - but it never goes below 18/19 even when off for half the day. A lot of the time certain rooms don’t even kick in for a boost at night.
Upstairs set at 19 and that will only very rarely kick in at 4am for a little boost..
New barn conversion airtight as I could get an old barn, plenty good Enough for me! Id have put in MVHV for sure but ran out of space literally everywhere as it’s not a big building.
I put aircon in the two main bedrooms for summer as upstairs is half in the roof space and they get really hot!

 

[V8Druid]

21C??? ...... you lot live in the tropics .... our's is rarely above 17C and comfortable ... wood burner boosts things in the winter

 

[Regy53]

as i say i need to look at it in more detail, this morning the heating wasnt on when i got up and it was about 19 degrees in house but it felt a cold 19 degrees if that makes sense so going to need a morning blast . It must be pretty air tight a house given its rating and all that but its a huge old space at about 4000 sq ft.

 

[Regy53]

21C??? ...... you lot live in the tropics .... our's is rarely above 17C and comfortable ... wood burner boosts things in the winter

yeah i know right, i feel the cold with my back i suppose, i personally am happy enoguh at 18-19 and wood burner but i have kids and all that. In our old house we ran the heating twice a day to 21 and the inbetween was set to 18 and very rarely kicked in