Steps to take on self build

martyc5674

Hi there,
Thinking of building a 2 storey farmhouse type house in kerry after being offered a fab site.(circa 3000Sq ft 5 bed)
I have done a good bit of building myself in the past in our own house...built a garage have done all our plumbing have knocked internal supporting walls etc etc all stuff ive managed to do myself 100% without help bar plastering.

However im not prepared to do really any of this with the new build...i know its just too much to be taking on plus its an hours drive away.

I want the house to be as insulated as possible, as airtight as possible and i would like to have heat exchangers on the vents.
Another thing we would like are concrete floors on the first floor.

Is there an obvious choice as to the fabric of the shell of the building and the roof?
I had a quick trawl through the posts and i see people on about different cavity widths/fills/single skin with insulation on the outside etc etc.

I doubt we will be going with underfloor heating as it takes a while to heat up/cool down and realistically we will be both out @ work all day.

Cheers,
Marty.

Jimbo

Would you consider an externally insulated blockwork structure?
The blockwork (probably 215mm standard or aerated) would generally be suitable for supporting the concrete floor while the thermal bridges associated with cavity wall construction junctions would be eliminated.

You can then be generous with the insulation thickness to achieve a low uvalue.

You need to be careful to choose a competant installer with this construction as the devil is in the detail and there is no cavity to fall back on if water manages to penetrate through.

imitation

martyc5674 wrote: »

Hi there,
Thinking of building a 2 storey farmhouse type house in kerry after being offered a fab site.(circa 3000Sq ft 5 bed)
I have done a good bit of building myself in the past in our own house...built a garage have done all our plumbing have knocked internal supporting walls etc etc all stuff ive managed to do myself 100% without help bar plastering.

However im not prepared to do really any of this with the new build...i know its just too much to be taking on plus its an hours drive away.

I want the house to be as insulated as possible, as airtight as possible and i would like to have heat exchangers on the vents.
Another thing we would like are concrete floors on the first floor.

Is there an obvious choice as to the fabric of the shell of the building and the roof?
I had a quick trawl through the posts and i see people on about different cavity widths/fills/single skin with insulation on the outside etc etc.

I doubt we will be going with underfloor heating as it takes a while to heat up/cool down and realistically we will be both out @ work all day.

Cheers,
Marty.

As you have no doubt guessed the choices are endless, its easy to drive your self crazy, I myself have looked into many options, as have other family members who have built in the past. After going through it all we reverted to relatively simple systems, in many cases because while novel ideas, like quinnlite blocks are good in concept, they bring other headaches.

For the building material, I`m not too sure, I was always set on blocks myself. Id research the options and pick what suits you best.

For the insulation your first port of call should be a energy rating assessor. You`ll need to decide on what rating you would like, personally I went for A3 / B1, this winter aside I think Ireland is temperate enough that it doesn't require massive insulation. I also think that theres a threshold you`ll reach where you just wont make the up front money back in energy bill reductions. Dont forget to look into triple glazing and other glass insulation techniques, its all well and good if your wall has a U value of 0.2 but 40% of your house is glass and has a u value of 1.5 !

Heat recovery systems usually tend to be centralized, with ducting running back from each room to the heat exchanger. I think its well worth it from what I have seen, not just for heat savings, but for air quality and condensation control.

beyondpassive

Marty,

If you have yet to submit a planning application, you have a great oppertunity to use design to achieve energy efficiency. A compact design with good solar orientation, and none of the sticky on pointy bits that you see on pattern book plan houses, should help you deliver a house with passive level comfort for conventional build costs.

Thankfully we're getting past the idea of having to completely heat up a house twice a day, the current thinking is to maintain a stable temperature with a minimal heat load. In simple terms careful design and detailing, good insulation and cold bridge reduction, airtightness and heat recovery ventilation will help you achieve this. Thankfully the days of mindlessly lobbin insulation boards into cavitys and between rafters looks like being over, particularly for people who want to live in the houses they build.

martyc5674

Cheers lads for the few replies...im open to anything as long as it doesnt blow the cost out of the water...we have no design started and are thinking of a pretty straight forward "square" house like an old farmhouse...so no pointy bits!!

With the single block someone mentioned..im guessing @ 215mm that its block laid on the flat?...that would be a hell of a lot of blocks!!
And then how does the insulation "stick"...is it sprayed on or is the whole thing shutterred and poured?

Quinlite blocks i aint gone on..not good for hanging pictures and big tellys off!

What are peoples thoughts on superwarm houses?..im guessing if i went with one i would lose my concrete floors but if i beefed up the rafters and installed plenty of noggins could i get similar sound insulation??

Cheers,
Marty.

onq

Hi martyc5674

<SNIP>

I understand that a dormer bungalow we completed last year with high levels of Rockwool insulation in the roof, masonry cavity external walling with internal warmboard and full fill cavity insulation, with steel and concrete composite flooring, underfloor heating and a heat exchanger unit has achieved an A3 rating.

In relation to your build, you might consider using a steel structure with concrete 1st floor and a highly insulated skin.
There are also a lot of threads on boards.ie with competent comments by qualified persons for you to consider.
<SNIP>

ONQ.

<SNIP>

Edit: Please stay on topic and refrain from putting on post caviots, there are enough provisors in the charter and on Boards.ie in general.

justflow1983

martyc5674 wrote: »

Cheers lads for the few replies...im open to anything as long as it doesnt blow the cost out of the water...we have no design started and are thinking of a pretty straight forward "square" house like an old farmhouse...so no pointy bits!!

With the single block someone mentioned..im guessing @ 215mm that its block laid on the flat?...that would be a hell of a lot of blocks!!
And then how does the insulation "stick"...is it sprayed on or is the whole thing shutterred and poured?

Quinlite blocks i aint gone on..not good for hanging pictures and big tellys off!

What are peoples thoughts on superwarm houses?..im guessing if i went with one i would lose my concrete floors but if i beefed up the rafters and installed plenty of noggins could i get similar sound insulation??

Cheers,
Marty.

Theres no reason you'd have to lose the concrete floors, as long as its inside the thermal envelope it won't contribute to heat loss. It will, however, store a lot of heat which is good for thermal stability but will mean that the house takes more energy and time to heat up if you allow it to cool.

There are a lot of alternatives to the concerete floor. Acoustic layers in a timber joisted floor can block a lot of the sound transmission. There are also steel joisted floors, as well as solid timber floor slabs called Brettstapel. A good carpenter and a sound absorption layer should be all you need to avoid sqeaking and hearing footsteps.

I'm a big fan of timber frame: its fast to build, it doesn't require much wet trades, can be prefabricated, its natural and easy on the environment, and lends itself to energy efficient building methods. It performs well when you're maintaining a steady temperature, and if you build it right is very resistant to dampness problems. Its definitely worth looking at if you're not committed to a blockwork house.

martyc5674

justflow1983 wrote: »

Theres no reason you'd have to lose the concrete floors, as long as its inside the thermal envelope it won't contribute to heat loss. It will, however, store a lot of heat which is good for thermal stability but will mean that the house takes more energy and time to heat up if you allow it to cool.

OK..Im a bit confused here though as i thought concrete floors and timber frame didnt go together?


Can you remind me of the layers/sequence for timber frame?
I was of the opinion that the outside of the house was 1 leaf of block and then within that there was a membrane then a timber frame which supported joists etc and also housed the Insulation.
All this was then covered in plasterboard from the inside.

Cheers,
Marty.

justflow1983

Timber frame and concrete floors aren't something I'd mix. I was just pointing out that concrete floors wouldn't really cause any problems with energy efficiency if you were doing an externally insulated masonry build. I just got off the redeye from New York so I'm kind of incoherent.

Modern timber frame techniques should not use the external layer of blockwork outside of the timber frame. In fact, timber frame is meant to be an alternative to masonry construction and the idea of a blockwork outer leaf is a local adaptation to the Irish building industry. People here were sceptical of wood houses when they were introduced, as well as preferring render cladding, so the block leaf is used as substrate for the render as well as reassuring the homeowner that their house is "tough" enough. When timber stud construction (called wood light framing in the States) was developed in the 1860s, it was meant to be clad in painted wood or render over a wooden lath. At the time, is was used where the only available building material was wood that was milled locally.

Today you would have a timber stud wall, with insulation between the studs and another layer of rigid/semi-rigid insulation externally. Then you have battens to the outside of the external insulation and either timber cladding or render onto a render backing board. There is a weather membrane between the external insulation and the battens, as well as a vapour control layer to the inside of the assembly, between the plasterboard and the studs.

Construct Ireland has a lot of relevant information on timber construction, as well as woodspec.ie and buildingscience.com

justflow1983

martyc5674 wrote: »

I doubt we will be going with underfloor heating as it takes a while to heat up/cool down and realistically we will be both out @ work all day.

This thermal lag will be the case in a building with lots of concrete inside the insulated envelope, regardless of heat source. The only real difference is that with radiators you'll feel some of the ambient heat directly from them as soon as the heat is turned on, but the building will remain pretty cold until all the concrete/masonry has been warmed up. However, if all of this thermal mass is located inside a very well insulated envelope, it will contribute to a very stable internal temperature and should stay fairly warm.

martyc5674

Cheers for those replies Justflow...very insightful.
Im aware of thermal mass and its charachteristics.
Marty.

justflow1983

If you're interested, this article here has a slide for timber framing instructions from 1854 (first image):
http://www.buildingscience.com/documents/insights/bsi-030-advanced-framing

In 1854 they didn't even use racking sheathing. It was just timber studs on 18" centres and then horizontal wood cladding holding the whole thing rigid.

It must be noted that the framing technique in this article is specific to North American practices and doesn't reflect the movement in Europe to a "vapour open" approach to materials outside of the internal vapour control layer.