air conditioning for heating? or separating 1rooms radiators

[greensusie51]

We are looking to heat a flat roofed 5m x 5m x 8ft high extension to our house (already built), which will be used as a study/garden room.(I work from home) it has 2.5m wide double glazed patio doors:south facing.

We want it to be heated seperately from the house, (as I dont want to heat the whole house when I'm working in here all day) and someone suggested an air conditioning unit.

This somewhat confuses me as we want it primarily for heating, not cooling, do air con wall mounted units heat just as efficiently as cool?

Is this more efficient than just extending our gas heating/radiators into the extension or is this air conditioning unit really a viable alternative?


If extending pipes /rads into new extension is the best option is there a way we can separate this room from the main house circulation so we an just have the radiators on in this one room in the day?

any advice on either option appreciated

Look forward to hearing from you

 

[chrishutt]

Forget air-con unless you really need the cooling capacity. You could extend your heating system to feed a radiator, but you might have to take the flow and/or return right back to where the pump or boiler is so that it can have an independent zone valve control.

 

[HarrogateGas]

Air con is definatly the way forward for you, it does heat almost as effienctly as it cools, also in summer it is nice to have a nice air cnoditioned office/work place.


Only last weekend i installed air con to my entire three bedroomed semi detached house and ripped out the central heating. I cant afford the on going gas prices and this air con (I have 5 cooling/heating fans in the house now) not only serves me proud when its minus 10 degrees outside but also when its 38 degrees outside too........its a doddle to install as well.

 

[fender]

I totally agree with the above, it's now very cost effective to run and very quiet compared with the older systems.

 

[chrishutt]

...this air con (I have 5 cooling/heating fans in the house now) not only serves me proud when its minus 10 degrees outside...

A heat pump using ambient air as the heat source is going to struggle with outside temperatures below +5°C, let alone -10°C! That's the problem with using air conditioning as a heating as well as a cooling system. HarrogateGas may be sorely regretting ripping out his gas heating come December!

 

[fender]

Most modern systems will cope with -10c these days. It's part of my trade and I've installed hundreds of them.....

 

[chrishutt]

Most modern systems will cope with -10c these days. It's part of my trade and I've installed hundreds of them.....

So you'll be able to tell us exactly what their performance is at, say, 0°C. How much power do they consume and how much heat do they generate?

 

[fender]

I'll try to look it up tomorrow Chris.

 

[johnb80]

I've had aircon / heatpump installed in my house for the last 15 years plus. I haven't had a problem heating during the coldest winters, I have recently replaced 2 units with more modern ones and the performance of these was even better. I do still have gas central heating, the primary reason for aircon was summer cooling, it was nice while the brats were young to switch off the central heating when they had gone to bed leaving the aircon units to heat the remaining used rooms. Certainly for south facing room it would be good and I'm sure you will get plenty of heat in winter time.
Look on ebay for aircon units, get ones that have known components such as toshiba compressors etc.
Regards - J

 

[chrishutt]

But it's a question of cost. Electricity is about 3 times the price of gas, allowing for the gas to be burnt at 90% efficiency in a condensing boiler. A modern air source heat pump operating with mild external temperatures of around 15°C will have a COP (Coefficient Of Performance) of say 3.5 (so 1kW power input produces 3.5kW heat output). The heat pump is therefore slightly cheaper to run in mild conditions.

But when it's really cold outside the heat pump COP drops dramatically, so gas heating becomes a lot cheaper. And of course the amount of heating required is much greater with colder external temperatures (4 times as much @ 0°C compared to 15°C), so even if low temperatures (average 0°C) only occur for say 1 month in 8 of a generally mild heating season, that month will still account for around a third of the total heating requirement.

To put it in simpler terms, at 15°C external temp £1 spent on powering a heat pump will deliver slightly more heat than £1 spent on fueling a gas condensing boiler, but at 5°C you get more heat for your £1 with gas, and at 0°C and below you get a lot more heat/£1 with gas.

 

[greensusie51]

Thanks everyone for all opinions, facts and figures I didn't realise my question would start such a debate!

I think we will try it for a year and keep a tab on costs. Hopefully the south facing patio doors will help bring some sun's heat in during the day which is when I will be using this room.

I will try and remember to post next year the realistic costs

Being in east anglia, winter daytime temperatures hopefully should be a bit warmer than Yorkshire!