House renovation sustainable energy - overwhelmed!

sheena36

Hi there, 

We are currently renovating a detached 4 bed chalet bungalow and are at the stage of trying to decide upon which energy source to use for the house. 

We have a fair bit of land around the house and are on top of a hill in Northern Ireland with other houses not too close, so we are in the very fortunate position of being able to have a few options open to us. 

The main problem is there are so many avenues to consider, so many mixed reports for each, and constantly changing advice. 

We would like to do whatever is cost effective (we are already stretching ourselves with the cost of the renovation) but also what is going to be as kind as possible to the environment. 

We initially had intended on getting ground source but our builders are advising against it as they have had some bad experiences with clients and that is putting us off.

Has anyone got any experience or advice in this area? We would be very grateful to hear it.

blueacid

It's probably quite a bit of overwhelm, there are so many different heating / energy saving / heat storage methods available.

There are several points to consider here. The first and most important is to ensure that whatever source(s) of heat you go for that you aren't squandering the heat you get. Make sure that your house is built, as best as possible, to retain the heat. I'd suggest having a read up on enerphit standards; see what you can do to ensure that you retain the heat as much as possible rather than having it vanish with draughts and poor insulation.

This work will then mean that technologies like a heat pump could come into play. They're powered by electricity (so if you later add a wind turbine or solar panels you can make use of the power you generate to cut down on the heating bill).

There's sometimes a bit of confusion in terms of how they work and how they get seemingly mad efficiencies. Rather than a fan heater or bar fire (which has to generate all the heat from the electricity going into it), they move heat from one place to the other. They can be air-source (ASHP), or ground-source (GSHP); ground source requires a fair bit of digging at some cost, but the payoff can be greater efficiency in the winter. Air source is cheaper to install since it doesn't require a load of digging, but because the temperature a metre or two underground is a fairly steady 10c, a ground-source model can be more efficient than an ASHP in winter.

Regardless of the source of heat for a heat pump, the other consideration is that they get more efficient when the change in temperature they're being asked to produce is smaller. If you've got a ground source heat pump and you desire 35c water (ideal for underfloor heating!), you'll get much greater efficiency than an ASHP outside in -5c being required to produce 60c water. Correspondingly, they aren't a drop-in replacement for many gas boilers. It's desirable to run the heating for longer at lower temperatures than a 2 hour searing blast morning and night. As a consequence of the lower temperatures, it's best to opt for underfloor heating, or if that's not possible, larger or extra radiators might need fitting with 22mm piping to make the best of the lower flow temperature from a heat pump.

There's a lot of technical jargon behind the scenes, one to look out for is the COP. Stands for Coefficient of Performance, and is a lowish number, typically up to 4. This lets you know how much energy the heat pump is moving, per unit of power going in.

A worked example: if I have a 1kW bar fire and run it for two hours, I'll use 2 kilowatt hours of power and gain 2kWh of heat energy in the house. If I have a heat pump which uses 1kW of power but which has a COP of 3.5, if I ran it for the same 2 hours I'd get 2 x 1kW x 3.5 = 7kWh of energy for the same money. This is where the 'cheaper to run' arguments come from.

A higher COP might only be attainable with a lowish radiator temp of 40c. If I set the heat pump to go to 60c instead, the COP might drop to 2. The precise numbers are often in the datasheet for a given heat pump. The precise trade-off in terms of cost and effort to install (might you consider new radiators? hiring a big ol' digger for putting in the ground source piping? underfloor heating pipes with new concrete screed on the floors?) needs balancing against the potential higher running costs of not doing these things (eg if you just stick with small radiators and crank an ASHP up to 60c and end up with a feeble COP).

The overall benefit of moving to a heat pump is that you then have the option to disconnect any gas supply, and you don't then need to worry about delivery of fuel to the house or that fuel being stolen (Oil tanks, wood piles, and the such).

I hope this has helped somewhat, and that it has not further confused you!

QrizB

This is a much shorter reply!

Someoine asked a similar question yesterday, looking for advice on greening their energy use. I suggested they start with the Energy Saving Trust, there's lots of useful info on their website:
https://energysavingtrust.org.uk

If you want personalised advice, scroll down this page to "looking for advice where you live":
https://energysavingtrust.org.uk/about-us/contact-us/

markin

Solar will never off set your power use for a heat pump even if you can go big say 15KW peak and production would be in the summer with little in the winter when needed.

If you own some woods or can start growing a small forest a wood stove would be the cheapest and it works in a power cut.

What is your current heat, mains Gas, oil, all Electric?

sheena36

Thank you all for your responses. We have a little wood, and are planning 3 woodburners for the house. Currently the house is oil, no option for gas. We had considered the ground source,  ut had been reconsidering swaying towards a potential turbine due to the builders' advice. 

The house really is getting stripped back to bare bones so we have an option to change to whatever is most appropriate. We are planning for underfloor heating, however we are concerned the cost of this will be crazy! 

ProDave

If you are doing a FULL renovation then do it properly and upgrade the insulation and air tightness aiming to get up to or close to passive house levels.  That will significantly reduce your heating need and low heating need offers other options like air source heat pumps.

And living on a hill without many neighbours means you are one of the few cases where installing a wind turbine might actually work and can offset your electricity use (it will never provide all of it)

If you want help and advice on a proper renovation, seek out the BuildHub forum.

Flight3287462

Had ground  source for 11-12 years on a Nibe Fighter system installed by an installer that knew what he was doing (in fact he was the only person on the whole build that did what he said he was going to do, when he said he was going to do it).

We have a relatively small three bed room two storey house well insulated to the standards at the time and we use 9,500MWh/annum of electricity.  

Make sure you get the correct spec of heat pump for the house, install underfloor heating and heated towel rails job done.  Only thing I would change is we but a thick engineered floor down (against advice) I would now go for the thinner engineered floor if I were to do it again - slightly more efficient.

Use the wettest piece of ground you can find for your array.  We have 700m of pipe at 1m depth on two runs that cover an area of 40mx40m or so. Living in west coast of Scotland means the ground runs wet which is a big bonus (you should be similar).

Take all the warranty you can get.

markin

The heat loss from 3 vented fires would work against the heat pump, so I think you have to make a choice.  to most people a full renovation doesn't always have a budget for full internal or external insulation when it should, even more importantly for heatpumps.

ProDave

markin said:

The heat loss from 3 vented fires would work against the heat pump, so I think you have to make a choice.  to most people a full renovation doesn't always have a budget for full internal or external insulation when it should, even more importantly for heatpumps.

I don't think the OP is talking of open fires, that would indeed be madness if you are trying to make an energy efficient house.

We have a wood burning stove but crucially it is room sealed.  That means it draws it's combustion air directly in from the outside via a duct pipe and not from the room air.  So when it is not burning it is not a constant source of heat leaking up the flue.  It really does not seem to hamper the very low energy requirement of our house and is a useful free source of heat some of the time.

Only 1 stove is enough, that will heat the whole house when it is lit.  Indeed it MUST heat the whole house, if you shut the doors to that room and stopped the heat circulating to the rest of the house, that room would very quickly overheat.  And ours is only a small stove.

sheena36

Thanks all, just to confirm, appropriate insulation is top of our priority list.

It's quite a large house, the wood burners would be sealed units and would be used in different rooms at different times. We have one in our current small semi-detatched and are well aware of the need to open the doors! The intention would be to rarely to have all 3 running at once. The main open plan living dining kitchen will have a wood burning stove and this is where we see us spending most of our time in the house. 

The main query is in regard to the decision between oil/ground source/turbine for which I thank you for all of your input. 

There is still conflicting reports regarding the quality of installation and those warranties you talk about @Flight3287462 - you seem to have had a great set up, I've heard others haven't been quite so fortunate with ongoing issues, companies going bust, expensive/impossible to fix if anything does go wrong. 

Various ways to skin this cat, just hoping to make sure our investment will have some sort of longevity. 

markin

The are threads in the sub forum on room sealed fires still having slight drafts and becoming cold so I imagine 3 could add up to quite the air leak.