Heating and hot water for granny annexe

[bhm1712]

If there are going to be diggers on site (probably), what about a ground source heat pump?

But will that provide cooling in the summer?

Does that matter?

Last time I checked most houses don't have air conditioning installed and gas central heating doesn't provide cooling in summer either....

 

[EFLImpudence]

But will that provide cooling in the summer?

It's for a Granny in Britain.

 

[ban-all-sheds]

But will that provide cooling in the summer?

Yes.

https://en.wikipedia.org/wiki/Geothermal_heat_pump

 

[ericmark]

It seems callus, but you do have to consider for how long will it be used 24/7? The caravan and boat stuff is not as economical as normal house gear, but it is small, and in some cases cheaper. My caravan always has electric huck-up, but still water and central heating, both carver are gas powered from a gas cylinder. There are also oil powered units which we used in the narrow boat. The Eberspacher heater we had on the boat heated water, and through a Calorifier (heat exchanger) it did the engine, domestic washing and domestic heating, and are very small, and compact. However because they are not as efficient as normal domestic equipment they are in theroy not permitted, simply because of the efficiency, and building regulation rules. Also wood burning fires in many houses, in theroy, are not permitted as you are only allowed a drop of efficiency of 5% so any house heated by any other form of heating in the past can't in theory use a wood burner, but of course they do.

Some of the latter caravans have the option of either gas or electric, and one has to consider the caravan only has a 16A supply. Caravans do have showers, but since you get water in a barrel from local stand pipe clearly designed not to use much water, we would always try to use showers provided by the site.

In essence the granny flat is very like a caravan in that the occupant can come to the main house to do some functions. And since better insulated than a caravan it should in theroy use less power than a caravan to maintain. One would hope correctly designed a small electric panel heater should be enough. In my mothers house we had a problem with temperature so have independent thermostats and timers for bed room and living room, using that method in theroy you should not need both rooms heating at the same time, so in theroy 1 kW is likely enough for heating. If that is the case then simple panel heaters would do the job, but powered from a thermostat and timer. For a 20 year time then having gas piped in and full central heating is likely the best, but for 5 years then likely simple panel radiators.

I have same problem, my mother at 91 is at the moment living in he own house on her own with carers 3 times a day, to convert garage to a granny flat possibly it will only be used for a short time, however she could live to 100 or more. However health wise even if she did likely she would need special care I could not provide so unlikely to use the flat for more than 5 years. Can't use house because she is in a wheel chair, and house not suitable for wheel chair use. So in real terms if her condition deteriorates only option is to go and live with her. However father-in-law is 89 and lives next door but one and he also needs care, so I would not be able to live with my wife we would have to live in separate houses. It is never easy. Once one dies then easy, but both in good health, but alzheimers is kicking in with both. At least my father-in-law has two other children, but life is never easy!

 

[pasty_girl]

Thanks so much again everyone - this is proving really useful

We didn't realise about the load of an electric shower so will talk to our electrician about the cost and practicality of installing that.

We will also look into LPG tank and boiler which we hadn't previously considered.

Ground source heat pump is going to be too expensive to install I think.

Many thanks for your reply ericmark - we will need to find a solution that meets building regs. Like you say the annexe will be v well insulated and therefore using two panel heaters with thermostats and timers may not have huge running costs. So our big question is how long would it take to "make back" the install costs of another method through savings on bills.

Ours is for happier reasons though as the annexe is for my brother and I suppose we want to think in terms of 5-10years as we don't know where life will take us all (I have children 0, 2 and 4). I am sorry for the difficulties old age brings - I recently lost my last grandparent so saw to some extent the pressures on my parents. It's not easy.

 

[davelx]

Air source heat pumps, that is inverter air con, work less well as the outside temperature drops and may not provide enough heating in very cold weather, so you need to take that into account when selecting the units.

 

[securespark]

If you feel brave you could build an earthship, you would need very little in the way of heating.

http://earthship.com/a-look-at-the-models-of-earthships

 

[pasty_girl]

Ah that looks fab but sadly after a year wrangle with the planning department we won't be allowed a hair out of place when it comes to the appearance of it!!

 

[stem]

I would probably install a couple of electric storage heaters, and a hot water cylinder with immersion heater, all could be run on an off peak tariff such as economy 7 or 10 at approximately one third of the cost of the full daytime rate. If you get storage heaters with combined convectors that can be operated at any time, they are useful for when it's not cold enough to require a lot of heat, or for a brief top up in really cold weather.

Forget running domestic hot water from the main house it could take several minutes for hot water to reach the annex, well insulated pipes are good, but they won't keep the water useably warm for extended periods, unless you install a pumped ring main that continually circulates hot water in a loop (you will need a stored hot water supply in the main house for this to work)

Ground source heat pumps are good, but expensive. Air source heat pumps are cheaper but have two problems that ground source heat pumps don't have. Their efficiency drops dramatically when the outside air temperature drops down towards 5 degrees, and the outdoor unit also starts to ice up at this point and can use much of its generated heat thawing itself out.

Some find with heat pumps that utilise air as the transfer medium that the noise of the fans can be irritating, and that in heat mode, that they can dry the air and make it stuffy. Connecting them to underfloor heating pipes containing water will prevent this, but you would loose the cooling function and significantly increase the cost.

 

[pasty_girl]

Brilliant thanks Stem - some really useful information there. Sadly I don't think an economy rate will work for us as we are a family of 5 in the main house and all about during the day all the time (kids v young and husband working from home). Really appreciate the air pump thoughts we had been trying to work out that kind of thing re efficiency.

 

[stem]

Sadly I don't think an economy rate will work for us

During off peak times, (ie during the night) electricity is available at a cheap rate. So storage radiators heat up during the night whilst everyone is asleep, consuming the cheaper electricity. They store up the heat (which is why they are called storage heaters) and then automatically open up a vent when required and let the heat out into the room during the day. You can control when.

The hot water cylinder will also heat up during the night and the insulation keeps the hot water piping hot for you to use the next day.

All of this happens automatically, you don't have to be there.

Two tariffs are generally available, Economy 7 which is on for 7 hours during the night, and economy 10 which costs a bit more, but gives an additional 3 hour top up in the afternoon.

It won't effect the main house, but any electricity you use there during the off peak times would be charged at the lower rate.

 

[RF Lighting]

Out of all options available I'd put storage heaters stone cold dead last place. They are a dreadful uncontrollable way of heating a space and were historically used because there was nothing better.

Personally I'd go with the upnor underground pipe and extend the house central heating to the granny annex. It keeps install costs low as all you need is the pipe and a few standard radiators, there's no additional maintenance costs as youll have your boiler serviced any way and if you've ever seen the levels of insulation on that pipe work there's no risk of freezing and the heat loss will be so minimal it's not worth worrying about, and as already mentioned gas is much cheaper than electricity to heat with.

 

[just pumps]

Personally I'd go with the upnor underground pipe and extend the house central heating to the granny annex. It keeps install costs low as all you need is the pipe and a few standard radiators, there's no additional maintenance costs as youll have your boiler serviced any way and if you've ever seen the levels of insulation on that pipe work there's no risk of freezing and the heat loss will be so minimal it's not worth worrying about, and as already mentioned gas is much cheaper than electricity to heat with.

With a zone valve?

 

[Taylortwocities]

Out of all options available I'd put storage heaters stone cold dead last place.

Agreed. Along with the issue that you would have to engineer an Economy 7 supply to be run to the annexe. This would double up on the U/G cable as it is a separate supply.
Also, you would need to get an E7 supply provided in the main house, I'm assuming that you do not already have this?

 

[RF Lighting]

Personally I'd go with the upnor underground pipe and extend the house central heating to the granny annex. It keeps install costs low as all you need is the pipe and a few standard radiators, there's no additional maintenance costs as youll have your boiler serviced any way and if you've ever seen the levels of insulation on that pipe work there's no risk of freezing and the heat loss will be so minimal it's not worth worrying about, and as already mentioned gas is much cheaper than electricity to heat with.

With a zone valve?

Yes configured as a separate zone so the granny flat can have completely independent timings and temperature settings to the main house whilst still running off the same boiler.

Thinking about it, there's no reason why you couldn't then split this into two separate zones in the flat using one for central heating and one to heat a small water cylinder which could supply all the hot water and shower requirements.