Eco-heating options - pros & cons

YogiEdwards · Post by **YogiEdwards** » 01 Dec 2009, 13:31

Hello

I have recently bought a big old house in Cardiff. It needs lots of renovation and currently has no central heating, which to me is an opportunity to do something energy-saving.

I've had a regular plumber quote for a regular gas central heating system and an eco-plumber quote for various options including an air-source heat exchanger, under-floor heating, solar thermal hot water & a wood pellet boiler.

The biggest difference is the cost – the heat pump/underfloor heating is about £9K more expensive than the regular option and solar thermal hot water is another £10K. At current gas prices, the payback period is about 14 years – though I fully expect gas prices to rise dramatically in the coming years. Still, it’s a lot of money to shell-out up-front to put my money where my mouth is & feel warm & fuzzy about saving the planet.

I’ve eliminated the wood pellet boiler option as this could end up a bit of a Betamax technology if it’s impossible to find supplies of wood pellets in a few years time. The other possibility is these boilers become so commonplace as fossil fuel prices go through the roof that the price will come down.

Something occurred to me regards the heat exchanger too. If it runs on electricity, that means no heating in a power cut. Plus I’ve go no info as to electricity consumption/running costs. One website suggested that, as electricity is dirtier/less efficient than gas, it’s debatable whether a heat exchanger would have lower emissions than a regular gas system.

So I’m probably going to go for regular gas central heating/radiators/hot water. The price difference could buy me multi-fuel stoves around the house if the fuel situation got really bad later down the line.
I welcome other opinions as to the pros and cons of these technologies.

Keith

snow hope · Post by **snow hope** » 01 Dec 2009, 14:27

If you have access to wood logs, offcuts, pallets, etc. then consider a wood log boiler with large thermal tank. They are supposed to be good for bigger houses.

Kentucky Fried Panda · Post by **Kentucky Fried Panda** » 01 Dec 2009, 14:40

Your typical gas boiler has an electrical control system, so it won't run in a power cut either.

Personally, I'd go A rated gas boiler and supplemental solar hot water with extensive insulation throughout the house. Triple glazed windows and cavity wall insulation.

raspberry-blower · Post by **raspberry-blower** » 01 Dec 2009, 18:49

Haggis makes some good points - if the house is single skinned, though, go for external wall insulation.

Just as long as there are no "conservation issues" mind

phobos · Post by **phobos** » 01 Dec 2009, 19:30

Obviously also to consider how long you plan on staying there

Post by **adam2** » 02 Dec 2009, 08:41

Haggis wrote:Your typical gas boiler has an electrical control system, so it won't run in a power cut either.

Personally, I'd go A rated gas boiler and supplemental solar hot water with extensive insulation throughout the house. Triple glazed windows and cavity wall insulation.

True, but remember that the electricity consumption of a gas central heating system is very small and can be supplied from a small cheap generator or from an inverter.

A heat pump system uses a great deal of electricity, and in practice that means grid power only in most cases.

YogiEdwards · Post by **YogiEdwards** » 02 Dec 2009, 09:08

Many thanks for your responses.

Will be calling the plumber today.

eatyourveg · Post by **eatyourveg** » 02 Dec 2009, 10:33

Think about a Rayburn. Cooking, heating and hot water from one source, and the central heating can operate independently of electricity.
In a recent several hour power cut we did feel extremely smug. And warm. And we could cook and put the kettle on. All in the dark ha ha. No, that is when the stock of 10 gazillion candles came in handy.

Catweazle · Post by **Catweazle** » 03 Dec 2009, 10:51

I'll second the recommendation for a large thermal store if you go for a wood-fired boiler. I have found that when burning some wood my boiler puts out loads of heat for a short time and a large thermal mass would even out the bumps. This is more noticeable when burning softwoods or "light" hardwood, so would apply if you are thinking about burning pallets and scrap wood.

If I burn a dense wood like Oak or especially Hornbeam then there isn't a problem, it burns for a lot longer and is happier burning on a low flame, with the air supply turned down.

Adam1 · Post by **Adam1** » 03 Dec 2009, 11:03

I'd look at improving the insulation, making it much more airtight and removing or reducing cold bridges. Depending on the type of house, you may be able to make it a Passivhaus or near Passivhaus. That way, you'd need little or no heating. All that money and complexity on heating systems could be avoided.

This is the approach I've decided to go for.

Andy Hunt · Post by **Andy Hunt** » 04 Dec 2009, 17:39

raspberry-blower wrote:if the house is single skinned, though, go for external wall insulation.

Just as long as there are no "conservation issues" mind

http://www.powerswitch.org.uk/forum/vie ... hp?t=12728

Post by **kenneal - lagger** » 04 Dec 2009, 19:29

We heated this 2300 square feet house using a woodburning cooker and a gravity (pumpless) system using skirting radiators to the upstairs rooms and had another woodburning stove in the living room. It was well insulated though, having cavity wall insulation to the ground floor, 150mm of Rockwool in the first floor walls and 200mm of Rockwool in the ceiling and over the room in the roof. I would use more than that in the roof now. We extended this house from a bungalow in 1978/9.

I've recently designed three projects to Passivhaus standard, one of which has been built http://www.guardian.co.uk/environment/e ... e-ann-link, one of which is in the process of building http://www.greenhomediary.com and the other is still in planning. They all have external insulation and a wood burning stove for heating. The Winchester house will have a three panel PV and battery system to give emergency electrical power and solar hot water.

We have a 220 litre Albion Mainsflow thermal store with our woodburning cooker which works well and irons out any overheating problems with the wood burning stove.

£10K for solar hot water is a rip off. Try http://www.Navitron.org.uk for their evacuated tube system. It cost just over £1k for the kit, depending on the number of tubes, and they have a forum where you can pick up an installer.

Insulating a house removes many of the problems with heating supply by bringing the problem down to manageable proportions.

I've just noticed that another supplier has got "navitron.org" and is rerouting everything to their own website. Cheeky buggers!!

emordnilap · Post by **emordnilap** » 05 Dec 2009, 19:20

£10K for solar hot water? Eh?

I suppose gold-plating the fittings can't be cheap.

Look, Solartwin, you either love them or hate them. I love them. Works in powercuts, will not burst pipes when frozen, no anti-freeze required. We don't need it in winter because of the back boiler so the argument about evacuated tube vs flat plate has less force.

The cost? Three years ago €3,700 total including shipping to Ireland, 21% vat, a plumber for two days. Then I got €700 back as a grant.

Good luck with your £10K system, my friend.

edit: that price included an new hot water cylinder.