Spending free government money

Ok, the government Green Homes Grant. It’s £5k or £10k, and for me it’s £10k. You need to spend it on both a primary and secondary element if you want the secondary, and actually all I really want is the secondary, double glazing.

The maths is as follows: my windows will be £10k. If the primary element of the GHG is, say, £6k, then I will get £5k off that and also £5k off the windows, so the net cost is £6k rather than £10k.

The primary elements that could apply to me are solar thermal (solar panels that heat water) and air source heat pumps (basically air conditioning in reverse). I currently have a combi boiler.

Has anyone any experience of either of these two things? I’m leaning towards getting the air source heat pumps, because they can act as air conditioning in summer as well, but the only site available for the units is likely to be in the shade so they won’t do much, and I’m mildly concerned about the noise.

Does shade make a difference with air temperature?

I have only seen one installation in the flesh and it was butt ugly with a big white box in every room.

Is it possible to have one very large unit and have the warm air ducted about the house?

Another option would be air heat pump running underfloor heating.

I believe heat pumps need a really, really well insulated house to work as they run at a much lower temp than central heating. It sounds like a real challenge to retrofit. We put ufh into our house when we extended and in some rooms it is borderline because the room has old, not well insulated, external walls. And our ufh runs at 55 degrees, air pump systems run lower still

All these are very reasonable concerns. The house is a Victorian terrace that has been extended twice, so has differing floor levels, dodgy insulation etc. I suspect that the air heat pump might be a shit idea, I’ll have to manage my expectations when I get a quote I reckon.

Being in the shade should be good when the thing is running as air con, but bad when it’s running to heat the house. However, as you say, there will be a fan blowing air through it and the most important thing will be the air temp rather than, say, the temp of the unit’s casing or the patio slabs it’s standing on. It’s these secondary things which will be most affected by shade or sunshine.

Heat pumps are low average power devices. They work best if you can run them for long periods to slowly heat your well-insulated house. They’re a bit hopeless if you don’t want to heat the house in the daytime, because you’re both out at work (remember that ?) or through the night, because you’re both under the duvet, but you do need a 10-20kW blast for 90 mins in the morning and a few hours in the evening.


when we investigated you couldn’t get the grant for air heat pumps, unless your insulation was up to scratch. Insulation was also a primary element in the grant.

Insulation could be an issue. I have some loft insulation that I did myself - it’s 10cm thick and then the loft is boarded over. But their website talks about solid wall insulation - sticking on insulation to solid walls, that seems a real fucking pain.

A house near here did that, polystyrene sheets attached to the outside then painted. It looked really tidy to be fair but the Windows ended up quite ‘deep’ in the walls as they’d got 3 inches thicker

We have 100mm airtek block, 75mm rock wool then brick on the extension, we have 100mm polystyrene under the floor and the big room seems to stay at a fairly stable temp. You do feel every little draught though, make sure your windows fit (unlike ours)

The Uk really needs to get Scandinavian levels of insulation though, and better quality buildings. Insulation is really cheap when built in but when a 4’ sq cupboard counts as a bedroom every inch of wall thickness counts against their profit

I don’t think I’d be allowed it as it’s in a conservation zone.

I agree totally on new builds, given the knowledge we have now there is no excuse for not building things better, but everything is about profit rather than providing people with a decent place to live.

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Let’s sod the environment and make things unaffordable for no good reason. All they should focus on is appearance being in keeping with surroundings, but not at the expense of making places unliveable

Yep, you can get pretty much any configuration you want, if you prepared to lay out the dosh. VRV and heat-pump (variable refrigerant volume) systems with a single outside unit feeding multiple indoor units.
Indoor units can be mounted on the surface of walls, ceilings and floors. Or spend more to have concealed units in walls, ceilings or underfloor.
All of these types have internal motors so generate noise, however the best are pretty quiet in operation. For even less noise, a ducted system is also possible where the air handling unit(s) are hidden away and ductwork is concealed in floor/ceiling voids with just small surface grilles showing.

If your roof doesn’t have a big overhang at the eaves and (if you’ve got them) on the gable walls too then external cladding can look even stranger. The roof can be extended, but it’s more work. You also have to worry about damp. There have been nightmare stories of badly executed cladding preventing Victorian walls, where the damp was often kept at tolerable levels by the wall ‘breathing’ it out in dry weather, from doing so. Without a cavity it then appears in your ground floor rooms.


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Maybe I could get something that was fundamentally designed as air conditioning but would fit the grant requirements. The more I read the less I think the air pump would work as heating for me, but I would like air conditioning upstairs!


Knock up a dodgy invoice on your computer and buy a watch

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Our place was built in around 1840, solid walls, no roof overhang. We had a quote for air pump heating, external insulation including a roof change to cover. I would need to live here for the next 70 years to stand any chance of recovering the cost. We went to see a local instalation, that included solar panels. The bathroom was full of water tanks, they where having a water heater fitted so they could have a hot bath rather than tepid, and a large area of the garden/patio was unusable as the heat pumps blew cold air at it constantly
Modern well built well insulated places should work, but it costs way too much to apply everything needed retrospectively, and it still may not work well.


We have the 100mm external insulation and render, it is fantastic, the best money I have ever spent. I would say it paid for itself in 5 years and makes the house far more comfortable winter and summer. If properly fixed incorporating vapour barriers there is absolutely no problem.
As for the breathing :woozy_face:

For retrofit you will need a high temp heat pump. I’m doing a big project at the mo. 150 local authority homes will get them. They are being brought up to spec with loft insulation double glazed windows etc . Like Graeme said, the properties need to be able to hold that heat to make it work properly.

You may find with a normal heat pump that your existing radiators are undersized

There are some nifty heat recovery systems out there, but really need to be designed well with the rest of the building. Retrofit is again costly and still might not achieve the goal you want