Optimum new build house design for Heat Pump

Air Source Heat Pumps (ASHPs)

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MikeF

(@mikef)

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Topic starter 01/01/2026 5:22 pm

I have some friends who are in the enviable position of building a new house from scratch. They know i have a heat pump that works very efficiently in a new build Bungalow, and have asked what they should be saying to their architect with regard to their heating design.

The house will be over 2 floors, each about 100sq meters, 3 bedroom, built with insulation and air tightness better than building regs (without going silly). Situated in a rural area of Yorkshire, but not on the hills. They will initially be just 2 of them, but they are intending living in this house for 30+ years, so want to get it right 1st time.

The ground floor will be UFH which should be able to run at 30-35 degrees. What do i suggest with regard to the bedrooms upstairs? A well insulated house wont need a lot of heat in bedrooms, for a large part of the year, so putting in underfloor would seem to be an expensive option. However even with K3 rads these would need a higher water temperature which would then be detrimental to the whole house COP.

Has anybody got any suggestions about the best way for them proceed?

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Majordennisbloodnok

(@majordennisbloodnok)

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01/01/2026 5:41 pm

Whilst I'm not the best person for advising on house design for efficient heating, one thing does spring to mind. If ever there is an ideal time to consider MVHR, it's at the house design stage, so do get your friends at least taking a look at heat recovery options. The more you can conserve heat whilst maintaining reasonable ventilation, the less work the heat pump will have to do and therefore the smaller the heat pump that needs to be installed.

Additionally, albeit not something for the architect, if they're going to be getting the builders in for that scale of work, the digger for the foundations could possibly also be used for digging trenches in the garden for a ground source heat pump rather than an air source heat pump. Once again, just worth investigating; a GSHP will be more expensive but perhaps not that much more if installed at the same time as the house build.

One detail that is often overlooked, your friends might well want to get the home kitted out properly with structured network cabling (i.e. computer network sockets dotted around in the same way the leccy sockets are). It might not be that closely related to heat pumps and so forth but modern heat pumps, solar inverters, EV wallboxes and so forth are all Internet-enabled and wired network connections are far more stable and reliable than wifi, so getting said network incorporated right from the start is a good idea.

Now I've gone down several rabbit holes, I'll step back and let someone better qualified to talk about heat pumps jump in and answer your original question.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

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JamesPa

(@jamespa)

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01/01/2026 5:43 pm

Posted by: @mikef

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However even with K3 rads these would need a higher water temperature which would then be detrimental to the whole house COP.

Has anybody got any suggestions about the best way for them proceed?

From first principles I would say:

Definitely design for a single low flow temperature, not different flow temperatures.

Definitely calculate (to the extent possible) the heat transfer from downstairs to upstairs, and adjust accordingly. I get the impression most heat loss programs attempt to do this (given the right data) but only for conductive transfer not convection. With a big stair well convection is probably rather significant, but I have no idea how to calculate it.

Several people on forums report that, with a very well insulated house, no heating is actually necessary upstairs.

Possibly a bit of calculation and a bit of suck it and see if the convection transfer cant be calculated

I just noticed that @majordennisbloodnok mentions MVHR. 100% agree but but the heat transfer from MVHR will need to be factored in if air is moved between floors.

This post was modified 1 hour ago by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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