New Build

[TimR]

Trying to finalise how to heat my new house (hopefully to be built later this year) and have been considering all that I have read here and elsewhere and would like your opinions just to make sure I am on the right track.

House is 130m2 on 2 floors and is north facing on a north facing hillside in Invernessshire, insulation will probably be slightly better than current regs.  No mains gas and I want to avoid oil and LPG.

My favoured option is a gasifying log boiler with accumulator tank.  Probably tying in solar thermal to reduce the amount of burning we would need in summer.  I have included a 4x3 'boiler room' in the plans.
I have 3 or 4ha of woodland behind the house and plenty of further space where I would plan to plant a further 1-2ha of firewood (coppiced ash?) and have age on my side when it comes to the woodcutting work.

It would certainly not be the cheapest option but is it the best (worth the cost)?

Anyone running a set up like this in Scotland (ie gasifying boiler + solar) who cn point me in the direction of suppliers?

Tim

[camillitech]

Hi Tim,

can't really help much other than to say that I'm having a similar dilemma and don't want to use wood because age is not on my side  . What I can say is that I've been coppicing birch, well coppicing is probably the wrong word, more like sensibly harvesting for 22 years and you would not notice. I'm no expert on these matters but birch seems to be what does best at this latitude, or at least it does on the west side.

Good luck, Paul

Though I would insulate well past building standards.   

[qeipl]

Tim,

I went through the same process and have now been living in mine for a year.
You can see my conclusions here - http://www.navitron.org.uk/forum/index.php/topic,12434.msg137200.html#msg137200

With a new build spend the money on insulation, solar gain, etc. and you won't need any 'big' heating equipment.
Insulate twice as well as building standards. It's the cheapest, greenest thing you can do. And it will save you a lifetime of chopping wood.

I'm on Skye so similar latitude and climate to yourself.

Cheers,

Malcolm

[wookey]

Quite. Building to 'slightly better than current regs' at this time really isn't good enough. You should be doing at least AECB silver, and preferably much better. Spending a little more on insulation (it's not actually expensive), will save a fortune in increasingly expensive fuel (whatever you choose) over the next 50 years.

If you design it properly you won't need any heating at all, beyond a few-hundred-watt heater whien it's below -10 outside.

[TimR]

I have done what I can to maximise solar gain but being on the north facing slope of a big mountain I won't get quite as much gain as some locations.

The architects basic spec has u-values of roof - 0.15, walls - 0.22 and floor - 0.18.  I do want to improve on these standards but how much better should I aim for?  What is practical whilst still retaining 150mm studs?

I realise that air tightness also comes into it but, correct me if I am wrong, a lot of that comes down to quality of work done on site rather than what we specify at this stage.

Tim

[qeipl]

I have done what I can to maximise solar gain but being on the north facing slope of a big mountain I won't get quite as much gain as some locations.

The architects basic spec has u-values of roof - 0.15, walls - 0.22 and floor - 0.18.  I do want to improve on these standards but how much better should I aim for?  What is practical whilst still retaining 150mm studs?

I realise that air tightness also comes into it but, correct me if I am wrong, a lot of that comes down to quality of work done on site rather than what we specify at this stage.

A glass roofed utility room on the back of the house is a great way to capture some solar energy if you're north-facing. As are veluxes on the back roof.
Something like an Ecocent will move the captured energy to other parts off the house.
Unless you're tucked hard into the north slope of the hill you'll get lots of solar gain in March, April, May when the weather is still cold, and also in October, when things are starting to cool down.

My floor insulation is 200mm EPS fitted hard up against a continuous skin of 50mm EPS behind the plasterboard on the walls over the top of the 150mm studs. Roof is the same.
So I have 200mm EPS all round with no cold bridges (u-value 0.17).
I was on a very tight budget but if I was doing it again with more cash to hand I'd use foil-backed PUR insulation and make it thicker all round. That would bring the u-value down to around 0.13.

The continuous skin of insulation inside the framing makes air tightness much easier.

[dhaslam]

In a two story building the   walls are relatively more  important than floor and ceiling compared to a bungalow but it is easier to insulate the floor and ceiling.   I have 125mm PUR in the floor and the attic has both  glass fibre filling the 225mm  joists and 100mm PUR between the rafters.    The 150mm bead in the  walls goes up into the gables.   I think  that the insulated attic  probably has the  biggest effect on heat retention because the west facing sunroom that has a higher ceiling and lower roof,  with no rafter insulation,  is a lot colder.     Windows are 1.6 U-value but most are single pane with no opening section.

[djh]

I have done what I can to maximise solar gain but being on the north facing slope of a big mountain I won't get quite as much gain as some locations.

The architects basic spec has u-values of roof - 0.15, walls - 0.22 and floor - 0.18.  I do want to improve on these standards but how much better should I aim for?  What is practical whilst still retaining 150mm studs?

I would suggest that you look at wrapping insulation outside the studs. For examples, look at the designs by Viking House on the greenbuilding forum and at the Canadian REMOTE manual. There's lots of other useful info on that forum too. The idea is that you keep the studs warm, which makes the design simpler, whilst also getting continuous insulation that is easy to apply.

I realise that air tightness also comes into it but, correct me if I am wrong, a lot of that comes down to quality of work done on site rather than what we specify at this stage.

Quality of work on site is definitely important, and that needs quality supervision, but none of it is any use without a good quality design for airtightness in the first place.

Your architect should be leading you on these topics, but it sounds like you're having to push. Have a chat to another one or two to see if they're more aligned with what you want.

[wookey]

Look at a minimum of 0.15 all round. 0.1 is better and allows you to make a passive house, but as you get down there it's all about designing out the thermal bridges, rather than upping the spec for the good bits.

As djh says, the Green building forum is better for this sort of stuff, with enormous amounts of info.

[Brandon]

I would reiterate  what has been said by djh and wookey.

For airtightness I would have the continual layer around the outside, as this helps to keep the stud warm.

I have witnessed too many houses (3 in the last 12 months alone) where the client specified high levels of insulation, but were thwarted by incompetent architects and acknowledgeable builders.  Simply using lots of insulation does not make for a warm or draught free house, it needs to be done well and carefully by someone who knows and understands what it is they are trying to achieve.

I would advocate having an air tightness specified in the design (and a stringent one at that) so that when (I wish is was more likely to be "if" but experience dictates) the building under performs, at least if they have failed to meet that part of the contract then you can get some form of recompense.

I have a client now (for whom I have installed an integrated solar, oil, and wood heating system all running the under floor) who has rooms that simply do not attain the desired temperature.  Of course his first port of call for complaint was with us (we had during the course of the job pointed out several bits that were simply not up to standard, on the back of which he insisted that they take down the finished ceilings on the flat roof to remedy the celotex that was rattling between the joists in the wind!!), we then proved that the rooms were getting 4 times the energy that they allegedly required to heat them, and he is now getting legal with the builders.  The draughts through every part of the building fabric have to be felt to be believed, but there is nothing (as smugly pointed out by the MD of the building company) in the contract that states a level of air tightness that is to be obtained.  These are not the single crew knackered van type builders either, they are a highly respected local company with over 50 men on the books, all the nonsense accreditations and iso standards on the vans etc.

It beggars belief, but alas it happens time and again.  If at this point you are having to push, change your architect and get someone who truly understands, rather than someone who will just draw another 50mm of PIR and think that it will suffice.

A new architect at this point may cost a few quid, but will rapidly repay in spades when you are heating your house easily for the next x years.

As far as people to recommend for wood based systems, you should send lightfoot on here a PM, he builds houses too.

Regards

Brandon.