House Build help and advise greatly appreciated.

Munster_Munch

Hi all boardsters,

As you can see its my first post and I am a newly registered member. I have been on this forum hundreds of times as a visitor and have found it very helpful and informative.

I have just received fully planning permission for a 1.5 storey, 2400sqF house:).
Below I have outlined what I think is very well insulated house in the most cost effective way, that should be cheap to heat.
I am probably way off the mark here so any help, advise or contacts would be greatly appreciated for any aspect of the build.
The best price I got from a contractor so far for builders finish was 80euro/sqF.
I am probably going to do it direct labour due to cost but also down to the satisfaction of it when the house is complete, btw I am not connected with the building industry at all, just a rookie getting onto the steep learning curve of self-building.

Strip Foundations with 100mm insulation and power floated floor.
Cavity Wall: 40mm cavity with 80mm Insulation and to fix insulated slab to inner leaf.
Hollowcore upstairs with concrete stairs, all 4”block walls internally
Heating: Rads with gas condensing boiler and Solar panel for HW. Stove in Kitchen\Dining not sure with or without back boiler.
Electrics: Cat 5, Sat cable x2, co-axial in kitchen\Dining, Sitting, Conservatory and Master bedroom, would like central audio system depends on cost really

Sorry for the long winded post(I know there is loads I've left out, I wanted to get the main points out there), just trying to get stuff finalized, hope to start in 5-6weeks:).

Thanks.

Lantus

Part L of the building regulations outlines what you need to achieve as a minimum. Bear in mind though that it's way behind most leading european countries as we have historically a very poor record in setting good standards (and enforcing them.)

Adding even a extra 10-20% insulation can make a huge difference to your annual heating bills. Triple glazing can be sourced at very little extra cost to double these days. Even better, look at the Passiv Haus standard to see a house that requires no traditional heating sytem what so ever. Imagine being virtually free from energy price hikes in the future! (and that was developed in the 70's)

Air tightness is where you can make a huge difference. Specifying a rate of air leakage (AND THEN TESTING IT!) can slash your energy bills even if you dont go for the full passiv haus spec.

Builder can be very slap happy in putting in insulation poorley, ignoring cold bridges and basically lashing it in quickly and covering it up because you cannot see it ayway. A carefully written spec and enforced inspection by either yourself or an approved specialist would make a huge difference.

Remeber your creating something that will probably outlive you. Investing in quality (not a word synonimous with the Irish building industry) will pay dividends in years to come when the rest of us are crippled from exhorbitant gas prices.

Best of luck either way.

beyondpassive

Agree fully with the above. Put the emphasis on improving the fabric, eliminating the cold bridges and airtightness.

From experience the best way to ensure that there is some degree of quality on site, is to get some construction detailed drawn up, at say 1:5 scale.

Don't go to site with Planning drawings.

galwaytt

Munster_Munch wrote: »

Hi all boardsters,

As you can see its my first post and I am a newly registered member. I have been on this forum hundreds of times as a visitor and have found it very helpful and informative.

I have just received fully planning permission for a 1.5 storey, 2400sqF house:).
Below I have outlined what I think is very well insulated house in the most cost effective way, that should be cheap to heat.
I am probably way off the mark here so any help, advise or contacts would be greatly appreciated for any aspect of the build.
The best price I got from a contractor so far for builders finish was 80euro/sqF.
I am probably going to do it direct labour due to cost but also down to the satisfaction of it when the house is complete, btw I am not connected with the building industry at all, just a rookie getting onto the steep learning curve of self-building.

Strip Foundations with 100mm insulation and power floated floor.
Cavity Wall: 40mm cavity with 80mm Insulation and to fix insulated slab to inner leaf.
Hollowcore upstairs with concrete stairs, all 4”block walls internally
Heating: Rads with gas condensing boiler and Solar panel for HW. Stove in Kitchen\Dining not sure with or without back boiler.
Electrics: Cat 5, Sat cable x2, co-axial in kitchen\Dining, Sitting, Conservatory and Master bedroom, would like central audio system depends on cost really

Sorry for the long winded post(I know there is loads I've left out, I wanted to get the main points out there), just trying to get stuff finalized, hope to start in 5-6weeks:).

Thanks.

Like other posters I feel, I think this could be better. By dint of using hollowcore floors, there is potential for an awful lot of bridging, and it's a cold floor itself, which may work against you: what, may I ask, is the motivation for using it ?

Starting at the bottom, I think the strip foundations and power floated floor in a particular, is a poor detail for both bridging and airtightness reasons.

Airtightness is a big factor these days, and whilst passive house is an aspirational goal, it does bring a cost with it, as does triple-glazing. You will have to decide for yourself whether, in this latitude, that triple-glazing will bring you a measurable return. Don't forget that, like everything else, there's glazing and........there's glazing. A good quality double-glazed system may well out-perform another's triple.....

I think the view to take would best be described as 'whole house'...........

Munster_Munch

Thanks Lantus, beyondpassive and galwaytt for your replies, this is exactly the views and feedback I was looking for, to help make an informed discission.

Totally agree with airtightness, not fully passive house thou, (I think the cost involve to achieve fully passive house wouldn't be cost effective). I want to do the best possible job for my budget. Airtight and highly insulated should take very little to heat.

Quote by galwaytt:

strip foundations and power floated floor in a particular, is a poor detail for both bridging and airtightness reasons

What would be a better alternative?

Quote by galwaytt:

By dint of using hollowcore floors, there is potential for an awful lot of bridging, and it's a cold floor itself, which may work against you: what, may I ask, is the motivation for using it ?

I thought the hollowcore would provide better soundproofing, than timber joists. I work alot of nights so I was looking for the best option so I could sleep during the day without restricting what others in the house do.

Thanks for the replies please keep them and the suggestions coming.

beyondpassive

Passive house dosent necessarily have to cost more than conventional, after all its just focusing on improving the fabric. Developements in EPS formwork rafts and wide cavity foundations mean that you can build

A well known Irish builder is even doing timber frame with EPS. Cheap as.
see <SNIP>
hows your swedish?

I mostly specify 250-300mm wide full fill cavity, on rising walls where the top inner courses supporting the inner leaf are done as quinnlite to reduce the cold bridge. The roof is built with Softboard outside and OSB inside for windtightness and airtightness with cellulose of mineral wool blown in at pressure. This is the year when builders are taking a step forward to low energy buldings. Previously it was just build it the usual way and bolt on some renewables bull. A good approach is to aim for a nice tight fabric, no cold bridges, HRV, centralised or decentralised and thus your heating system becomes very simple and cheap to run.

Treble glazing is 10% more than double glazed. The cost of thermally broken frames is about 30% above standard. The price of high quality windows is dropping all the time.

Well put Galway TT, the 'whole house' or 'systems approach' is the way to go. rather than look at all the elements and components in isolation, using a passive approach alows you to identify the simplest cheapest measures to get stable occupant comfort levels with minimum plant. Its a no brainer. Investing in better quality workmanship and components has many benifits apart from thermal comfort. Better air quality, aestetics, daylight and longevity of your build.

galwaytt

Munster_Munch wrote: »

Thanks Lantus, beyondpassive and galwaytt for your replies, this is exactly the views and feedback I was looking for, to help make an informed discission.

Totally agree with airtightness, not fully passive house thou, (I think the cost involve to achieve fully passive house wouldn't be cost effective). I want to do the best possible job for my budget. Airtight and highly insulated should take very little to heat.

Quote by galwaytt:

What would be a better alternative?

Quote by galwaytt:

I thought the hollowcore would provide better soundproofing, than timber joists. I work alot of nights so I was looking for the best option so I could sleep during the day without restricting what others in the house do.

Thanks for the replies please keep them and the suggestions coming.

I'm afraid the thing about hollowcore = silent, and non-concrete = noise, is a myth.
It is entirely possible to build a very, very quiet floor, using a form of timber construction (Open Web Joists + suitable detailing, for example..). The UK in particular has much more onerous Building Control, and noise is a big issue in townhouses, apartments and terraced houses, and all are regularly met using timber-based systems. And they do actually test houses on site, it's not just a paper exercise.

Hollowcore is, imho a good solution for commercial/retail applications, allowing, as it does, for a freedom in design of structure. But it's not silent without good detailing anyway, and requires both insulation and levelling of floors, over, as well as suspended ceilings and insulation, under. It also requires heavier walls and foundations, so it brings costs with it, too. This is simply overkill in a domestic situation, imho, anyway.

As for the foundation, the problem there is that the junction between the floor and base of the wall, is exposed to the interior of the house. This is both a cold bridge and an air leak source. There are several ways to deal with this effectively, from a modified 'standard' raft foundation, to a dedicated, insulated foundation system. Either would be better. Separately, I like the fact that a raft is also waterproof - a good pokered 35N raft would avoid that whole footing/sub-floor junction.

galwaytt

beyondpassive wrote: »

Passive house dosent necessarily have to cost more than conventional, after all its just focusing on improving the fabric.

A well known Irish builder is even doing timber frame with EPS. Cheap as.
see Attachment not found. .

I have never seen a passive project, nor even a report of one, that did not cost more than conventional. "it's just focussing on improving the fabric" is entirely true. Improvement using better materials, and more care (=more time), = more cost.

That roof, and "cheap-as" ? If it's cheap you're after.......what about the quality ? And, why stick-build a roof like that onsite, when you buy it premanufactured, in Ireland, with even higher spec XPS, and you won't need airtight membrane inside at all ?? That and the fact it's 4x times faster to roof a building with it. A typical roof is fitted, weathertight, in 1 day.

beyondpassive

Ya Galway TT, good points

Workmanship = cost. true.

I think in some situations where where the cost ceiling is under €90 per square ft in East Ireland, innovative solutions which may not be as vapour permiable as we would like are justified. Good sealing of the vapor tight membrane or taped ply liner combined with a controlled mechanical ventilation system are critical. I wouldn't advocate stick build, but the frame can be delivered with insulation added afterwards. Agreed its a more fussy way of building than your system, but it allows for competition between frame suppliers.

now to do a condensation risk analysis of the attached system. Its going on a house going certified passive, designed with good orientation and compact form which is coming in at conventional prices.

<SNIP>