How to heat my Huse

matelodave

Two sorts of heat pump - Ground Source and Air Source. The ground source are more efficient and predictable but can cost a lot to install as you need to lay out the ground collectors and you need a large area to do it in - that may not be a big problem as you are starting from scratch and you'll have contractors & machines on site.

Air source look like air conditioners and extract their heat from the surrounding air - their COP is specified at 7degrees outside to a low temperature of 35 degrees. Decreasing the outside temp and or increasing the flow temp reduces the COP so the lower the flow temp the cheaper they are to run.

If you are starting from scratch them ideally you want the system designed with a flow temperature around 30-35 degrees. My ASHP works at about that at 10 degrees outside increasing to 40 when it's zero. We also don't heat our hot water tank above 45 degrees.

The more efficient the system, the higher the RHI although the government is slowly reducing the payments for RHI as the equipment gets cheaper, so the earlier you start the more you'll get.

I chose my ASHP despite RHI (it took 4 years before I started getting any payments). I estimate that my system runs at a COP of about 3, we pay 10.5p for leccy so a kwh costs under 4p for heating & hot water.

I get nearly £700 a year in RHI payments for 7 years (£4900) and our total energy cost for a year is about £800-£850 a year for an all electric 140sq.m detached bungalow that's not very well insulated (built in 1986). I estimate that hot water costs about £100 a year and heating another £300-£350. The other £400 is for cooking, lighting, washing, TV, computers etc.

Smiley_Dan

Ok, 300 m².

Let's be kind and say you build to AECB Silver standard - http://www.lowenergybuildings.org.uk/leb/technical-information/aecb-silver-performance-standard/ (this is a bit pessimistic really, but...)

That would mean no more than 12,000kWh per year required. If you considered a 180 day heating season that means 2.77kWh of heating per hour. You could easily achieve that with a couple of oil filled rads from Argos, no wet heating required, massive capital saving and ongoing maintenance saving.

In reality there would be far higher peaks and troughs, but I'm trying to point out the possibilities.

But AECB Silver is actually a pessimistic target for a new build - you could go for better than that such as Passivhaus.

What I'm trying to show to you is that you can avoid the question entirely.

I think people approach this in the wrong way because they don't realise what is possible. Don't ask "how should I generate energy", ask "how can I minimise what energy I need".

renex

Smiley_Dan wrote: »

Ok, 300 m².

Let's be kind and say you build to AECB Silver standard -(this is a bit pessimistic really, but...)

That would mean no more than 12,000kWh per year required. If you considered a 180 day heating season that means 2.77kWh of heating per hour. You could easily achieve that with a couple of oil filled rads from Argos, no wet heating required, massive capital saving and ongoing maintenance saving.

In reality there would be far higher peaks and troughs, but I'm trying to point out the possibilities.

But AECB Silver is actually a pessimistic target for a new build - you could go for better than that such as Passivhaus.

What I'm trying to show to you is that you can avoid the question entirely.

I think people approach this in the wrong way because they don't realise what is possible. Don't ask "how should I generate energy", ask "how can I minimise what energy I need".

you do make this option seem extremely viable, but what would this do to my carbon emissions?
also would i need to keep refilling them?
how much maintenance do they need?

Smiley_Dan

Your carbon emissions would be far lower than any other option.

They don't need refilling. They require no maintenance.

I am just using those units as an example. You could also look at air to air heat pumps. These are air-source heat pumps, but just heat air and don't use heat exchangers to water. They perform better and are much cheaper to install.

If you are interested in this type of thing you need to talk to a consultant who can guide you - an architect who knows about low energy building or similar.

renex

sorry for the bombardment of questions but,

how would i have hot water?
what do the rads run on if they don't need filling?
if i got air to air wouldnt i need loads of vents?
if i only used a couple of rads would that mean that some areas of the house would be hot and others cold?
how much better do the air to air heat pumps perform?
wouldn't that imply that my RHI payments would be lower?

renex

by the way thats 300m2 for the ground floor

Smiley_Dan

Oh, ok, well you would require yet more energy still then for your upper floor. Which to me is an argument to either downsize or go for a higher standard.

This does not cover DHW (domestic hot water). DHW is very different to space heating anyway and IMO the systems should be separated. For that there are a number of different options. ASHP pre-heat, solar PV or solar thermal all work well. Could have a log burner tapped into it (although chimneys make energy efficient building more difficult... not impossible but you have to make up for it elsewhere). Some are beginning to realise standing hot water is not a good idea and use the above for pre-heating and then an instantaneous modulated water heater when the tank is still too cool.

The rads I originally mentioned are just electrical, they plug into a plug socket.

Air to air moves the air out of the unit itself. You can have split units if the layout allows. They are a bit better than A2W but not massively.

Going back to the oil filled rads, in reality they are so cheap you'd probably want to buy a couple, see how you get on, then buy more if the heat wasn't spreading.

You can't get RHI with A2A heat pumps (to my knowledge).

Smiley_Dan

This is a good podcast to learn about the possibilities: http://www.houseplanninghelp.com/

Cardew

renex wrote: »

by the way thats 300m2 for the ground floor

So 3,200 square feet for the ground floor.


How many floors?


You are having a mansion built, with an architect designing it, and you are asking the most basic of questions, on an internet forum.


Mmmmm

Smiley_Dan

BTW... "huse" ... is this in Scotland?