Worth installing Heat Pump?

windsortg · 20 Oct 2021

I am planning on having an orangery built at the rear of my home. Planning has been allowed for this. We plan to have open access into the orangery from our lounge (no doors to go through from the lounge into the orangery) so that the orangery can be used all year round.

We have a radiator central heating system throughout the house and our boiler is located in the garage. For our orangery, we would like underfloor heating since the flooring will be tiled. We are not looking to install underfloor heating in the downstairs to our house due to the sheer cost and disruption that will occur.

For our underfloor heating (UFH) in the orangery, one option is to run new pipework (flow & return) from the cupboard where our Megaflow is located, into the orangery via a manifold. I have had some plumbers come over who have suggested this is the best method to allow for UFH in the orangery.

I have read up about air-to-water heat pumps and with the price of gas rocketing, would it be feasible and possible to have a heat pump installed just to heat up the UFH in the orangery?

muggles · 20 Oct 2021

Unlikely. The smallest available heat pump is about 5kW which will almost certainly exceed the requirements of your orangery, and heat pumps do not run efficiently when the connected load is smaller than their output. A split unit air conditioner could be a good option for you though

windsortg · 20 Oct 2021

Thanks @muggles. Stupid question but with a split unit air conditioner, how would that serve the UFH in the orangery?

jackthom · 20 Oct 2021

Apologies for the thread hijack, but talking of split units which have a fan assisted radiator in the room, would that sort of radiator be a way of coping with the low flow temperatures that heat pumps in general can deliver.

There’s been much discussion of how we’d need either very large radiators or UFH, along with improved insulation. Could fan radiators be a way around this or would even they be struggling to provide sufficient output?

muggles · 20 Oct 2021

windsortg said:
Thanks @muggles. Stupid question but with a split unit air conditioner, how would that serve the UFH in the orangery?

It wouldn't, it's an alternative option which would at least comply with Building Regulations, where UFH connected to your existing heating system is unlikely to do so

windsortg · 20 Oct 2021

@muggles - can I ask why UFH conected to my existing heating system would not comply with Building Regs? What would be the alternative method for heating my orangery if I am unlikely to be allowed to connect to my existing heating system?

muggles · 20 Oct 2021

Your orangery would need to commit with the latest version of Part L of the Building Regulations for insulation and energy efficiency in order for the system heating your main house to be extended into there, and most don't. I believe compliance can be achieved using the right thermally efficient triple glazing, low energy frames etc, but it's difficult and expensive to do. Some companies will tell you you can do it provided you have separate time & temperature control, but that was changed around a decade ago.

The alternative, and approved, method is to have a completely separate system. That can either be split unit aircon as suggested earlier, or electric UFH if you're set on having UFH (or both, of course). The idea is that you'll only turn it on when you're going to use it and so it won't be warming the world up when you're not in there. Heating connected to your main system is (allegedly) much more likely to be left running when you're not in there, which wastes energy.

windsortg · 20 Oct 2021

@muggles - the flow & return pipes from the boiler run up to an airing cupboard where the Megaflow and heating pump/control valves are located. The idea would be to take a feed from the flow & return pipes running up from the boiler, and for these pipes to run to the UFH manifold. The UFH would therefore have its own control & thermostat such that the UFH can be turned off/on independently from the main heating system.

Would this method still not comply with the latest version of Part L of the Building Regulations? I have heard from various sources that electric UFH is not reliable, a wet UFH system is better in the long run, and to electrically heat a floor space of 24 sq metres will be costly.

muggles · 20 Oct 2021

No, as per my earlier reply, simply having separate time & temperature controls was outlawed for conservatories/orangeries etc about a decade ago, unless that conservatory/orangery is constructed to comply with Part L of the Building Regulations.

Electric UFH is very reliable, but yes it will cost more to run than wet (although it's often much cheaper to install, so swings & roundabouts).

All that being said, it's your home and it's not likely to get inspected until you come to sell it.........

Passenger4 · 20 Oct 2021

Since heat pumps work on drawing in hot air / heat from air, how do they work in winter months when it's cold outside? ;

From my understanding they will not warm a house up or they will be ineffective due to the low temperature outside?

Yes we're told to insulate homes better but that's counterproductive because in the summer the houses will be much hotter due to the insulation!

Alec_t · 20 Oct 2021

Passenger4 said:
Yes we're told to insulate homes better but that's counterproductive because in the summer the houses will be much hotter due to the insulation!

Not so. The insulation protects the house interior from the worst of the sun's heat.

Harry Bloomfield · 20 Oct 2021

Passenger4 said:
Yes we're told to insulate homes better but that's counterproductive because in the summer the houses will be much hotter due to the insulation!

That depends. The better insulation will retain the coolness of the interior, but the the longer the warm weather lasts the more heat will makes its way through to the interior. For instance my place is well insulated, so I aim to have all windows and door closed during hot weather, in the day, then open them up to the cool of the night air. Waste heat from TV's fridges and occupation etc. will though be retained.

MJN · 20 Oct 2021

windsortg said:
I am planning on having an orangery built at the rear of my home. Planning has been allowed for this. We plan to have open access into the orangery from our lounge (no doors to go through from the lounge into the orangery) so that the orangery can be used all year round.

What do you mean by 'orangery'? It is an ill-defined ambiguous term which could mean a variety of things, often with varying levels of glazing that leads to equally varying levels of thermal performance.

With the reference to open access that suggests it will be meeting building regulations in which case the choice of heating system really is yours, just like with any other extension to your house. I am unclear though why you are considering a dedicated heat source for the UFH and not extending the existing system to supply it?

flameport · 20 Oct 2021

Passenger4 said:
Since heat pumps work on drawing in hot air / heat from air, how do they work in winter months when it's cold outside? ;

They move energy from one place to another.
'cold' is relative, even at freezing temperatures outside, there is still energy in the air.
A random example: https://les.mitsubishielectric.co.u...ultra-quiet-puz-monobloc-air-source-heat-pump works down to outside temperatures of -20C.

A domestic freezer will be full of ice, but check the condenser at the back on the outside and it will be hot. That heat is what's being removed from the freezer.

The people that complain about their heat pumps not working or being ineffective are those who have had them installed incorrectly, such as low flow temperature heat pumps shoehorned onto old radiator systems that were designed for high flow temperatures and poorly insulated buildings which previously had grossly oversized gas boilers.
The rest are those who have other agendas such as promoting the continued use of gas boilers, such as individuals who write articles for the Daily Fail condemning heat pumps and conveniently forgetting to mention that they represent a major gas boiler manufacturer.

Master of None · 21 Oct 2021

Looking at your other thread I think its the modern name for a conservatory.
https://www.diynot.com/diy/attachments/orangery-for-forum-jpg.247716/
The amount of glazing will be a massive heat loss in winter if it is fully open to your main home. Would you not consider a double glazed dividing door and provide frost protection only?
My electricity payment has just doubled because it is directly linked to the wholesale gas price because this is still how a lot of electricity is produced.
Its a fact that electric heating costs around 3-4 the cost of gas for the same output currently.
Its also a fact that Air source heat pumps have a COP factor of round 2-3 depending on quality and outside temperature.
So while the running cost of the 2 are getting closer the installation cost of a heat pump is very high.
If you think you will be in the house for another 20-30 years go the full hog with heat pump, solar and battery storage but the initial outlay is very high.
Personally if your heart is set on having this as an actual living space open to your home I would just plumb a couple of radiators to your current system. Probably against current regs but at least you can put them on frost protection if the cost is too high.

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Worth installing Heat Pump?

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