Green Building Forum - Design of new Eco Study Center

Design of new Eco Study Center

IDN101 — Tue, 14 Apr 2009 16:01:51 +0100

Hi to all,

I am currently designing an eco study centre. It is a very modest building with a footprint of just 50m2. The emphasis on this project is low energy / sustainability. I have a few questions regarding it's design and construction that I am hoping someone could help with.

External wall will be of two types:-

Walls to the south / east / west:

Thermally lightweight / timber clad:-

INTERNAL
12.5mm duplex plasterboard
150x50mm framework @ 400mm centres
100mm insulation between studs
15mm WBP ply sheathing on face of framework
moisute barrier
19x38mm vertical battens (at 400mm centres)
38x38mm counter (horizontal) battens
150mm wide vertical larch cladding
EXTERNAL

Other wall type is:-

INTERNAL
15mm 2 coat plaster
100mm thermal conc block
100m insualtion
100mm thermal conc block
Lime render (thickness?)
EXTERNAL

Roof:

All I know is that the client wishes for it to be an aluminium roof. Can anyone suggest a "green" system for the aluminium roof? I've thought about a composite panel type system (ie Kingspan, etc), bu I don't think that it's too green? Any pointers, links would be most appreciated.

Also:-

Triple glazed windows

Anyone point me in the right direction to a supplier of triple glazed windows, here in the UK.

Will probably have loads more questions over the coming days / weeks.

Many thanks,
Regards,
Ian

Design of new Eco Study Center

betterroof — Tue, 14 Apr 2009 16:58:56 +0100

I can't help with the walls so much, but the roof - aluminium is pretty un-eco to be honest... why do they want this? have they considered a green roof? or shingles? if it's being billed as an eco study centre, surely they want it to demonstrate eco building techniques? You could look at NBT for their range of complete building envelope solutions, they do great insulation boards for walls and roofs:

http://www.natural-building.co.uk/

For triple glazed windows try Internorm. they do really efficient triple glazed units afaik, not sure about price.

http://www.internorm.com/

Design of new Eco Study Center

Paul in Montreal — Wed, 15 Apr 2009 12:59:06 +0100

Posted By: IDN101INTERNAL
12.5mm duplex plasterboard
150x50mm framework @ 400mm centres
100mm insulation between studs
15mm WBP ply sheathing on face of framework
moisute barrier
19x38mm vertical battens (at 400mm centres)
38x38mm counter (horizontal) battens
150mm wide vertical larch cladding
EXTERNAL

This is OK, but not great. If you are using 2x6 framework (which I presume your "150X50 framework is - though it's more like 135x38) you could do 24" centres (600mm) rather than 400. This would significantly reduce the amount of wood required and also reduce the thermal bridges. You also have no vapour barrier in your wall - your moisture barrier is really an air barrier and you need a vapour control layer on the warm side of the insulation. Not sure why you need both battens and counterbattens to hold the larch cladding - just vertical strapping is sufficient. I think something like this would be better:

Internal
12.5mm plasterboard
1x3 strapping
foil faced foam board (12.5mm will do) this is both a vapour control layer and a thermal break for the studs
2x6 studs @24" (600mm) centres
Filled with 125mm of your choice of insulation - could be blown cellulose if you like
ply sheathing or OSB (make sure it's external grade)
Tyvek/Typar air barrier taped as per manufacturers instuctions
1x3 (19x60) horizontal strapping
larch cladding
EXTERNAL

As for an aluminium roof, if you want metal, steel is probably a better bet - though aluminium is certainly lower CO2 (and before everyone shouts "embodied energy" remember that pretty much all aluminium is produced using hydroelectricity).

Paul in Montreal

Design of new Eco Study Center

IDN101 — Wed, 15 Apr 2009 13:23:04 +0100

Many thanks P.I.M.

What a fantastic forum. Just ordered both Green Building Bibles from Amazon. Can't wait to get stuck in!

Regards,
Ian

Design of new Eco Study Center

PaulT — Wed, 15 Apr 2009 14:34:17 +0100

Before you go any further!

If you are in the UK you will need an SBEM caclulation as the primary means of compliance with Part L (J Scotland). This is in addition to achiveing the minimum insualtion standards and an air tightness test result of q50 <10 .

I expect that you will need a higher specification than the examples you gave, although heat loss through the floors, walls and roofs (at Part L2A standards) will be a lot less than you might expect (Ventilation, thermal bridging and windows being the majority of heat loss.

As a visitor/study centre ventilation design will be more a more critical factor than in a home as the required ventilation rates are double and the occupancy varies significantly.

Lighting is a big factor for commercial buildings and you will need a lighing design that meets CIBSE guidelines and also energy efficient both in specification and in usage (zones, occupancy and daylight levels)

the situation you are in is that the same assesment procedure will be applied for your 50m2 building or for a 500m2 building!

Design of new Eco Study Center

dickster — Wed, 15 Apr 2009 14:37:50 +0100

We're building our little house using I beams made of softwood and (what is basically hardboard) for floor, walls and roof. Cavity filled with recycled paper. Quite eco, might be of interest.

Design of new Eco Study Center

WatchIt — Thu, 16 Apr 2009 08:07:56 +0100

Why don't you look at using a multifoil on the timber frame walls? That BBA one has been used recently, it was a favourite on the stands of the timber frame guys at ecobuild anyway.

Would be a good vapour barrier and break the thermal bridging of the studs as Paul said, but i think it would also improve the air tightness and u-value you need as suggested by other Paul.

I assume this is more eco than Kingspan, but i don't have a clue on eco credentials, guess i just think it looks cleaner!

Design of new Eco Study Center

sipman — Thu, 16 Apr 2009 08:33:44 +0100

Ian

keep it simple just use SIPs, low u values and Airtight quick and simple

Design of new Eco Study Center

IDN101 — Thu, 16 Apr 2009 09:29:45 +0100

Can you please explain what "SIPS" are / stands for?

Thanks,

Ian

Design of new Eco Study Center

PaulT — Thu, 16 Apr 2009 10:18:17 +0100

Posted By: WatchItWhy don't you look at using a multifoil on the timber frame walls? That BBA one has been used recently, it was a favourite on the stands of the timber frame guys at ecobuild anyway.

Would be a good vapour barrier and break the thermal bridging of the studs as Paul said, but i think it would also improve the air tightness and u-value you need as suggested by other Paul.

I assume this is more eco than Kingspan, but i don't have a clue on eco credentials, guess i just think it looks cleaner!

I would never ever recommend multifoil (and I will not even start on isocyanate foams.

SIPS are a very good idea and suitable for an 'eco centre' as sucha building (in my opinion) should be super insulated.

But, as I have said the performance of individual elements does not matter as SBEM is the means of compliance.

Design of new Eco Study Center

WatchIt — Thu, 16 Apr 2009 11:28:30 +0100

Ok, Paul doesn't recommended isocyanate foams but he thinks SIPS are a good idea?

SIPS are Structural Insulated Panels, Kingspan make a lot of them. Urethane in Kingspan no isocyanate i know but same ball game.

Design of new Eco Study Center

Timber — Thu, 16 Apr 2009 11:28:54 +0100

Watch out for air tightness at the junction of the timber and masonary walls, that might be a tricky area to deal with.

As other have mentioned, the specs you gave are ok, but not super insulative.

Pauls suggestions would work well, although i would suggest that you have vertical battens of some thickness first (attached to the timber frame), to allow better drainage and ventillation down the cavity.

For the timber frame my personal perference would be....

plasterboard
25 mm service void formed with horizontal 25x50 mm battens and filled with insulation
500 guage poly vapour control layer (or reflective vcl for better performance) lapped and sealed everywhere
140x38 mm timber studs @ 600 mm c/c with full fill mineral wool or blown fibre
OSB/3 sheathing in whatever thickness required (likely 11 mm)
Reflective breather membrane
25x50 mm verticals battens
25x50 mm horizontal battens
Timber cladding

Another option could be

Plasterboard
25 mm service void with insulation and formed with horizontal battens
poly or reflective vcl
OSB/3 sheathing (whatever thickness required)
140x38 mm studs at 600, fully filled with mineral wool or blown fibre
50 mm wood fibre based insulation board
reflective breather membrane
vertical battens
horizontal battens
timber cladding

This second option will prove reduced thermal bridging, a good u value, and if you were so inclined, the vcl could be removed, and the OSB taped and jointed and sealed to act as the vcl, and have yourself a breathing wall. Although personally i would retain the vcl for easy of lapping joints etc.

As for metal roofing, just watch out for ventillation requirements.

Timber