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Pole barn house new build


Pole barn house new build

Posted 15 Apr '19 09:33 PM

Hi guys,

Im a new member to ecobob. We are looking to start building a pole barn style house on 2 acres in South Otago later in the year and i was hoping for some advice. We love the passive house ideas but dont have the budget for a certified passive house but want to make it perform as well as it can.

Im just finishing my building apprenticeship so will be trying to do as much as possible to keep costs down. Im trying to build something that performs alot better than the minimum building code stuff we build at work lol.

We will almost definitely go with a maxraft insulated slab, polished concrete floors apart from bedrooms, 140mm framing with as much insulation as possible. Ecoply barrier around entire house. Hoping to strench the budget to a heat recovery ventilation unit.

My questions are am I missing anything major that Ive overlooked? What do people recommend is the best insulation performance vs cost? Do you think i should be using a air tightness wrap eg Intello?

Any questions or comments greatly appreciated

Brennan

RE: Pole barn house new build

Posted 30 Apr '19 12:58 PM

Hi Brennan.
I’m far from an expert but can share a little of what I know. The good thing us that you are using your budget to get a better performing house and not just a bigger house.
If you are thinking of getting a mechanical heat recovery ventilation (MHRV) unit then do everything you can to create and airtight or conditioned space. Taping the ecoply joins is a start but then you have to think of creating a gasket between the sheets and bottom plate and then how to create an airtight barrier around the top plate and across the ceiling. Maybe a wrap in place of ecoply depending on your bracing requirements.
The other area worth considering is investing in thermally broken windows (double glazed is fine) and have the thermal break in line with your insulation. You will just have to detail the flashing and weather tightness to the satisfaction of your local authority.
I’m not convinced on polished concrete floors but it depends on the design and how much of a heat sink it will be. I don’t know enough to comment further on this.
Avon Electric apparently do a MHRV unit tat is more economical than some of the European models but without some of the added features. Could be an option.
All the best but go for quality over quantity and have fun doing it.
Hayden

RE: Pole barn house new build

Posted 02 May '19 04:30 PM

Sounds like you are on track. 140 framing and insulation is getting to PH standard and you are well and truly above the NZ standard.

Our biggest expense was windows, triple glazing is nice and we have no issue with cold or condensation, even the inside of our windows feel nice to touch in winter rather than cold, but it comes at a cost. Biggest heat loss from windows I think. Avoiding aluminum windows otherwise thermal loss in winter.

Even Passive houses will need some form of heating in the dead of winter when you get 3-4 days of cloudy freezing days, what do you plan to use as heating back-up

RE MHRV,There are a few around, we ended up purchasing WOLF MHRV, mainly as it was the only MHRV on the market in NZ that had the option of a 1 KW heating unit, to warm the cold outside air, as our internal temperature dropped. Others like Zhender and the NZ MHRV may now have followed to keep competitive if not already.

RE: Pole barn house new build

Posted 05 May '19 04:09 PM

Thanks Hayden and ern for those helpful replies.

Hayden whats the best solution for stopping air movement between the slab and bottom plate?

Ern id love to go triple glazing but at this stage were probably only going to be looking at double glazing and really good full length drapes.

Our biggest decisions are around which are the best places to spend our limited budget for the best results between more insulation and air tightness and MHRV, central heating and solar panels etc.

As far as heating Ive been thinking about installing a solar evaporated tube system on the roof to supply us with hot water for dhw and underfloor heating and maybe a couple of radiator towel rails in the bathroom with a stove with wetback for winter back up or those wet misty winter weeks.

Brennan

RE: Pole barn house new build

Posted 07 May '19 05:17 PM

Hi Brennan,

I was in a similar situation to you - I liked the idea of a passive house but discovered it's a very expensive route if you still want to have a large-ish house! In the end, we have settled for a "pretty good house" that uses some passive house principles.

We are using the Pro Clima airtightness system. Only 90mm framing, but with the 45mm service cavity it brings the insulated space to 135mm and an insulation R value of 4.2 - and basically cancels out any thermal bridging through the studs or dwangs (this is critical in passive houses).

If you're willing to look beyond timber framing, you could look into building with monolithic materials such as SIPs or cross-laminated timber, etc.

If you only use EcoPly, you still face the problem of not having a fully airtight home, with moisture still potentially entering your wall cavities through air gaps - under skirting boards, through power points/switches, screws through GIB, etc. Also, my question would be, how effective is EcoPly when it comes to moisture getting through it? Plywood is hygroscopic, but I believe EcoPly has some sort of weatherproof coating on the exterior. Worth investigating, anyway.

The best MHRV systems (typically German - Wolf, Stiebel Eltron, Zehnder) are installed entirely within the home's thermal envelope. If the ducting runs through an unconditioned attic, like the many cheaper "non-passive-house" systems, you are losing heat in winter and gaining it in summer ($$ wasted and less-than-ideal/comfortable performance). The best systems also extract moisture from wet areas (hence they are balanced - no need for any other extraction fans).

Hope that's somewhat helpful

JR

RE: Pole barn house new build

Posted 18 Sep '19 10:25 AM

Hi Guys

Im back again. After doing a heap of reading Ive come up with a design an a plan on how to hopefully achieve the insulation levels I want without breaking the bank (hopefully).

Im going to use 140mm framing with either ecoply or rab board on the outside and tape the joins as a rigid air barrier. I will install r4 pink batts between the studs and over the rigid air barrier I will install 40mm PIR sheets like these ones

https://insulation.kiwi.nz/

to give me a thermal break on the studs. Then screw on cavity batterns before cladding. I will use a similar technique for the roof.
Does anyone see any issues or problems with this kind of set up?

Im pricing up a Zehnder unit for ventilation and triple glazing is on the nice to have list at the moment but that will be a budget decision.

Heating is proving to be the biggest sticking point. I was originally keen on a fire but I don't want a chimney breaking my thermal envelope. My wife loves underfloor heating especially since we will have some polished concrete but i dont want to spend heaps on a system we hardly use if my insulation works as well as I hope it will. That would just take money away from another areaof the build.

Any thoughts, problems, ideas, comments on any of this would be appreciated. This is an awesome forum.

Thanks
Brennan

RE: Pole barn house new build

Posted 18 Sep '19 02:31 PM

Hi Brennan,

Firstly, I'm not a builder nor an architect (not even close), so I really can't comment on how the combination of these materials would function.

I do know, however, that the main problem with airtightness and beefing up insulation becomes 'breathability' (i.e. the structure's ability to get rid of moisture). Building wrap used in 'code' builds is very hygroscopic, in that it easily allows moisture in the wall cavity to pass through it to the outside. I don't know enough about EcoPly, RAB board or PIR insulation to comment, but I suggest finding out if you haven't already. Having said that, if you go with a decent MHRV system, it should regulate the amount of humidity in your home anyway.

Insulation works best if the air around it is still. Think about wearing a polar fleece in a southerly (useless). But as soon as you put a windbreaker over the top and zip it up tight, you're toasty. The insulation in your walls and ceiling works the same way.

Here's a diagram: https://s3.amazonaws.com/greenbuildingadvisor.s3.tauntoncloud.com/app/uploads/2018/07/25054937/convection.jpg

If you are wanting to beef up insulation while cancelling thermal bridging, take a look at what the Zero Energy House did:
https://zeroenergyhouse.co.nz/walls

They put their nogs on the inside of the studs to create a cavity, to which they then added more insulation. It might be a cheaper way for you to achieve what you want (allowing more money for glazing/MHRV system). This with a taped RAB could be a good route.

Underfloor heating might be a good idea for South Otago. Note that it is not very responsive, in that takes a day or two to heat up/cool down, and it can be expensive to run, depending on the size of your house. You also have to insulate at least the edge of the slab if you go that route. I looked into it (for Canterbury) but decided it wasn't worth the expense since we were already building a thermally efficient house. I opted for a floor-mounted heat pump and a MHRV system. I also opted for a Cupolex floor, which has a higher R value than standard Rib Raft/EPS pods.

RE: Pole barn house new build

Posted 18 Sep '19 08:31 PM

Hi Brennan.

JR1 makes some good points. People I have talked to that own a well insulated house say they don't use underfloor heating much so might be worth some more research.

With regards to your wall envelope construction you just need to figure out where your dew point will be. Not sure on the science but there are suggestions that with standard timber frame construction with glass wool insulation and either a rigid air barrier or standard building paper that the dew point sits between insulation and RAB/building paper which is not what you want. You can use something called WUFI to work out where the dew point is. A European thing that I don't know much about.

Triple glazing should give you an R value above 1 but also comes with sound insulation qualities. Make sure the thermal break of your glazing sits in line with you wall insulation.

Shop around for the MHRV unit. I got estimates from 7k to nearly 15k for a 3 bedroom house. Even Avon Electric in Chch do a heat recovery system. http://www.avonelectric.co.nz/frames/recovery.htm

Keep us posted as it sounds exciting. Good luck.

Cheers
Hayden

RE: Pole barn house new build

Posted 06 Jun '20 06:43 PM

Hi Brennan, we can supply all bespoke Aluminium double and triple glazed thermal break windows and doors in a variety of colours and styles, at highly competitive pricing direct from our factory in China, we have AS 2047 certification. just send us your plans and or window and energy schedule for a quote.
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