Have you installed one?
Any first hand recommendations (I can use google myself) for information sources or suppliers? Maybe grants? Self-build experinces?

cheers

This is the leading guide I believe.

Considered one, looked into it, but decided against because of cost.
May consider an Air Source unit – bloke in the village has had one fitted.

Do you have enough land to go out or enough money to go down?

Looking at the cost per kW, ground water would probably work best for us on a potential project – also have space for horizontal pipe

Are you off the gas main? GSHPs don’t have a massive environmental benefit over a gas-fired condensing boiler, once the carbon cost of generating electricity at a power station is taken into account.

There was a user here whose floors I went to look at. I’m sure he was installing one for UFH. I’ll see if I can dig out his details for you. Nice chap. Sure he wouldn’t mind you emailing him. I’ll ping you a mail as soon as I get mrs deadly off the pooter.

Sent from my iPod Touch

No gas.
alternative to oil or elec.

cheers DD

Sent from my Computer what’s in front of me

😛

Sent from my iPod Touch which can now handle smileys better than my pooter

Stoner,

ygm

Sent from my iMac Biggest Screen Ever (not handling smileys though)

Ha, I know Al very well and he’s local. Had no idea he’d done that.

Cheers DD, shall give Al a call.

Sent from the O2 phone on the bog

Size the ground loop very conservatively (e.g. always go for the larger figure) would be my opionion, especially if you want hot water from it as well as space heat.

Get a georeport from the BGS to assess ground conditions, and read Karl Oschners book on heat pumps (called geothermal which is a bit misleading as GSHP are technically solar derived) to get some ideas.

use underfloor heating or large low temp rads

Cheers Tim,

yep, already planning a very large horizontal array, underfloor heating downstairs, and upstairs low temp rads.

cheers for the book tip, off to amazon…

EDIT: jeez,. £50 for the book… would it give me enough info to install my own system? – in which case it will pay for itself… (I’m a competent jobber and will be working with a builder)

They aint that green – I would probably go with a wood chip or, even better, wood pellet boiler instead… so long as you have a reasonably local supplier of fuel that is!

I think GSHP get’s hyped a lot as it is a techy solution, and something people can get all excited about in magazines and the like. Me… wouldn’t bother (unless I bought an old watermill and could then drive the pump from the mechanical water wheel… that would rock!)

Why do you want to install one? Is it a new build you are going for as well, since with good design you can massivly reduce the level of heating you need (to zero if you are really keen). Get your heating needs down, pop in some solar hot water with a wood stove as back up and job done 😉

I like RobS – he thinks like me.

GSHP/ASHP are good if you are off mains gas, and do have running cost and carbon savings. They are more expensive to install, run and emit more carbon than using mains gas however. If you MUST have central heating they are great BUT it already concerns me that you are fitting radiators upstairs – a decently insulated and airtight house would not need them.

Go for envelope first – masses of insulation, great airtightness, pay real attention to thermal bridges and thermal bypasses. Fit (assuming your airtightness is very, very good) a mechanical ventilation heat recovery system (MVHR), fit (water) solar panels and a gert big tank; THEN think about heating systems.

Having said all that, if you are on an old building thats hard to treat, go with GSHP.

Go speak to the green building forum guys as well.

This is a conversion.

We have the opportunity (and intention) of constructing to very very low U values and I want to use a utility room that can house alternative energy/microgeneration/water recovery systems and be upgraded/replaced with ease.

The building is on Elec only and Im trying to avoid Oil.

Also have easy access to large external area for excavation and will have a digger, so can lay pipe arrays to my heart’s content 🙂

Main problem is building volume.
At traditional cubic metre/14 = kW it’s a huge figure.
But I cant find any advice on how that denominator comes down if you build to very low heat loss spec as Im guessing “14” is for a pretty standard house.

Wood pellets are about 4p/kwh
assuming GHSP are, say conservatively 2.5 (they quote 3-4) x efficient using grid electricity to pump, then its something like 14/2.5 = 5.6p /kwh going down to 4p /kwh – and all without the hassle of pellets 🙂

We’d also use elec to boost immersion.

Im trying to avoid roof mounted stuff because of Bats and limited voids access 🙂

We had a heat recovery system in a previous house. Worked well.
Again problem with ceiling void access for ductwork from bathrooms etc. But possible.
Rads would only be needed if I though we needed the KW, I cant find much help on calculating KW with high efficiency buildings with UFH though 🙁

Rads would only be needed if I though we needed the KW, I cant find much help on calculating KW with high efficiency buildings with UFH though

Are you thinking about wooden floors or stone over the UFH Stoner?

In some rooms it will be carpet (around 2.0-2.5 Tog) and others wooden flooring.

others wooden flooring

Grand, I realise you’re handy and do your research, but watch yourself with the flooring over UFH, can be a bit of a nightmare if things aren’t specced out prawperly, like.

there’s so much material out there it can get so confusing.

Im now getting interested in the whole pellet boiler thing 🙂
expensive kit though £5k for 34kW… 😮

BTW – we have the benefit of laying a brand new concrete floor so makes life a little easier on the UFH…

But the price of eleccy is probably going to go up 😉

I just don’t like GSHPs (and I like air source even less!) and you are right to be conservative with efficiency ratings (I have heard lower than 2.5x talked about at CAT – alas my notes are packed at the moment so I can’t really quote but I think they were talking 2x was a reasonable expectation… could be wrong though!!!!)

Take your point on roof mounted gubbins. In that situation I would be looking even more towards woodchip/woodpellet. If I had the space that would be my heating mechanism of choice, and if anyone pulls off a micro CHP one it would be even better!!!! There is talk of fuel cell boilers (being trialled in the US I think), but they are probably too far away to be of any real interest at the moment.

When you are getting the place all insulated up remember you need to keep some uncovered thermal mass – it doesn’t count if you have insulation stuck onto the inside of it, or carpets. Verandahs and stuff to prevent excessive solar gain in summer months are really good too. I would also be looking into stuff like window placement if it isn’t too late to reduce heat losses as far as possible. I did have some ace modelling software for determining thermal performance, but alas my licence has expired and I aint paying for it again!

Its really interesting getting into designing buildings to work with the environment – I am big into very efficient design rather than relying on technology to “fix” poorly designed and built housing. Did my thesis on ancient buildings and how they were designed to work with the prevaling climate efficiently – and then comparing them to modern builds which are massivly compromised.

To calculate the power you require for heating is easy, you take the U-value of each component of the house (i.e. windows, walls, roof etc) and multiply each by the area of each one. So 10m2 of double glazed windows with a U-value of 2.2w/m2k would be 10×2.2=22w/k. Add all these together and you have a power required to heat the building to 1 kelvin above the outside temperature. You want to heat the building to 25K above external air, so multiply this by 25. That’s your “fabric loss” in Watts.

Then you need to add the loss due to infiltration, which depends on the house construction and airtightness. I would assume 0.8 air changes an hour for a new house, so 0.8ac/hr / 3600s/hr x vloume of house (m3) x 25K x 1.2KJ/kgk (Cp of air). Add this to your fabric loss and you’re there. I can help if you want, it’s my job.

GSHP is good if designed well, otherwise it’s rubbish. It wont be very efficient heating your hot water either. Have a look at dimplex, viessmann and ciat, they all make domestic heat pumps which are suitable for hot water. Look at the CoP charts in their brochures, you need to be above 2.5 to save carbon.

juliancottrill at googlemail dot com

cheers guys very helpful.

Rob – ive bveen “fantasizing” abvout building a low impact house for a few years now. The opportunity has arisen to do a barn conversion which, while it would prevent me from implementing some ideas I had on layout, does mean I can still have a look at “off-grid” and low running cost systems and tech.

Im not nearly well enough informed to get it optimised, and budget may well not get as far as a consultant to make up the difference, but a bit of research, keeping it simple and with a fair eye logical design I think I can get some of the way there.

Julian – thanks for the calcs help, I shall have a play. We (my builder) and I are going to be reviewing U values and materials choices soon.

This could all be for nought though as we need to buy the original site still. But at least it might not be all wasted as we have the interest now to keep looking for opportunities to do it anyway, even if this one falls through.

It makes a nice chain to turn my hand at a private residential development project instead of the £billion corporate schemes I spend most of my time on 🙂

When you are getting the place all insulated up remember you need to keep some uncovered thermal mass – it doesn’t count if you have insulation stuck onto the inside of it, or carpets.

BTW Rob, what’s that ^

I’ve got a ASHP , a Daikin one, 7KW. Bluddy fantastic thing it is as well. Set at 19 degrees it heats a 3 bed house in < 30 minutes, wood house with a reasonable but not amazing level of insulation. Costs about $50 pm to run.

Thermal mass is basically dense material that is open to the air – it soaks up heat when the air temperature is high and then slowly releases it as temperature drops. If you use it well it can help maintain a comfortable temperature (it’s why old houses are often cool in the summer, the reason that they often feel cold in winter is because modern living doesn’t really work with that particular style of house which was “lived in” all day long… so the fires were always running in the cold!) If you can get a flagstone floor in, or the odd unplastered wall opposite a south facing window, or a polished concrete/limecrete (in preference) floor – it basically acts as a big thermal sink to draw in the heat from either your central heating or solar gain and then release it as air temperatures drop… kind of stabalising temperatures.

One of my gripes with current building regs is that they obsess about keeping places warm at all costs, but there is nothing to keep them cool. Modern buildings are lightweight with little or no overhanging eaves and large areas of glazing, which is a really good way to make a house that is uncomfortable in warm weather… given climate change I really think this is missing a big point, and if you are building a house that you plan to live in long term I would pay a lot of attention to coolth as well as warmth. If you insulate on the inside of a wall that makes a building light weight btw, even if it is made out of solid stone, which is why I also don’t like these insulative panels that are sold to rennovate old houses!

Don’t get me wrong – warmth is still a deeply important thing in design, but I think the focus is waaay too much on that. Actually it goes beyond temperature too, if you start looking at the holistic “health” of a house then things get pretty complicated… but its an idea worth looking at.

There is a pretty decent book on all things eco-build: The Whole House Book

http://www2.cat.org.uk/shopping/product_info.php?cPath=46_47&products_id=788&osCsid=a9729fc3f5ea6d630385d19d1d083635

If you browse through other books in the CAT catalogue there are loads of interesting things. Stuff like passive solar design is very interesting, and something I would be really interested in implimenting myself. The Green Building Bible is probably worth looking at as well.

BTW Rob, what’s that ^

I think the answer Rob would give to the question I think you’re asking would be along the lines of the following…

Basically when it comes to living in a space, you want a comfortable temperature. This means reducing the range of temperature to a median, thus avoiding extremes of hot and cold. The means of achieving this are heating, cooling, and, insulating. (For the UK, we’re primarily considering insulation and heating, unless you have vast expanses of south facing glazing, which is a nice asset, but you might need to consider cooling or shading at times). Now all that is pretty obvious.

Judging from what he’s posted above, Rob and I would say there are 2 relatively straightforward ways of achieving this aim. Rob or Matt will probably explain better, but anyway…

1) Use a lightweight structure that is well insulated (usually) on the interior, thus the space can reach a comfortable temperature quickly with additional heat (people, appliances, heating systems…). No energy is wasted heating up the structure or subsequently passed to the outside. No significant heat energy is stored within the structure.

2) Use the thermal mass of the structure to minimise the amount of heating needed. Materials with a decent thermal mass (concrete, clay, some brick, stone…) store heat over a length of time. Heating a space (through occupation, appliances etc. as before) constructed with such materials takes some time, as the mass absorbs heat. However, this heat is also stored and then released into the space (and the exterior) as the space cools. In this way, the thermal mass can contribute to regulating the temperature of the space.

Typically, you’ll find many buildings in the UK (recently at least) have been designed with neither of these basic principles in mind. Often, they feature little or no insulation on a structure with inadequate thermal mass to round off extreme lows/highs in internal temperature. This leads to various problems, both for the building, comfort and health of the people using it.

Anyway, hopefully that helps you get into the ideas behind what RobS is getting at. If you have thermal mass (you mention concrete floors), use it. If you cover up all your heat storing materials with insulation (internally) then it can’t help with maintaining a steady(ish) temperature. Massive construction can also be more straightforward to detail than a rigorously insulated solution. You can also insulate a massive construction externally, thus benefiting from both temperature regulating massive elements (but you need someone who knows what they are doing, as moisture/ bridging problems are difficult to get around in some cases, as are aesthetic considerations). A staggeringly obvious hybrid, such as a massive internal construction with a lightweight well insulated skin, ideally with passive heating through south-facing openings in the façade is such a simple principle, would be ideal in many situations but is very rare to find (at least in the UK).

Neither principle can always be applied to existing built fabric, but understanding some of the basic ideas and how they might apply to what you’ve got might help you come up with some solutions.

Sorry for the long reply, but it might be of some help, and apologies for patronising if it’s not what you were asking. [edit, too slow, seems Rob beat me to it- also Birkhauser/ Detail series are germanic based publishers who have a lot of good stuff in both German and English that is worth looking at].

guys, thanks so much. Loads to digest. its late (builder buddy and I have just finished doing QS numbers) and we had wine to hand.

Im going to go through everything you guys have said again tomorrow with a towel over my head and take it all on board. thanks for your help.
and those that have emailed, well may get annoying emails back asking silly questions soon 🙂

Right. Got the hang of thermal mass now.

This conversion might well lend itself to some of those techniques.
The outer shell is 340mm brick, we have a choice of internal structure and were initially going with 200mm wool and thermalite in the walls with that thin 200mm equivalent foil stuff under the roof felt.

There is also a substantial glazed south facing opening that can be used to heat a concrete floor (or even relocated stone slabs if they can be recovered) – although I think it’s too much glass on the plans and could turn into an uncontrollable greenhouse….

But I shall go and get that eco book and look at what it says.

Stoner, interesting thread. We have just got planning permission so was looking at the same kind of questions as we want to go very green.

In Scotland the planners specify that we have to build timber framed, with stone or whatever external skin, as this is proved to be the most thermally efficient. Although we have no option, would be interested in people’s comments

We are also going GSHP as we have plenty of land. Was thinking about a wind turbine to at least provide enough power to run the pump for the GSHP, so all heating and hot water would be “free”.

Stoner,
Give me an e-mail and I’ll send you as much info as you could possibly want.

If your interested in taking the passive solar heating and Thermal mass to its limit you guys should look up Earthship for more detail. A technique for building / living completely off grid in New Mexico. They utilise many of the subjects highlighted above. A number have been built in Brighton and a demonstration project in Fife as well as one recently covered by Grand Design’s in France. Building Regulations and planning permision are very short sighted and very frustrating as they don’t grasp thermal mass as a concept at all.

Personally I think it is a brilliant concept that could and should be used to influence the design of all new / renovated houses.

Its my plan to build one in Devon over the next few years but I am expecting a very long and protracted argument with planning / building regs.

cheers guys.
Backhander, YGM.
Ta.