Single Skin Timber Frame

Ray Dow

Hi,

I've been looking at single skin timber frame details and they all seem to recommend a layer of 60mm rigid insulation external insulation.

e.g. plasterboard - VCL - insulation - OSB board - 60mm insulation - breather membrane - render/cladding

Can anyone advise why this additional layer of insulation is needed? I have never seen it detailed in a timber frame cavity wall nor a timber cladded wall

e.g. plasterboard - VCL - insulation - OSB board - breather membrane - cavity/ventilation void - brick/timber cladding

Thanks in advance

beyondpassive

It's needed to avoid the repeating and no. Repeating thermal bridging.

engineermike

Hi,
I would advise caution when assessing single skin systems. Noteable failure in our climate of certain systems.
I would be looking for a fixed ventilated cavity & avoid balconies in the construction all together.
See IS 440 for reference.
also :
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1669,en.pdf

I have seen complete system failure in as short a space as 5 - 10 years after construction. Insurers such as Home bond won't touch them with a barge pole.
I'd adopt specialist consultancy when assessing a system for use in Ireland.
rgds
Mike f

Ray Dow

beyondpassive wrote: »

It's needed to avoid the repeating and no. Repeating thermal bridging.

Any ideas why it's not recommended for timber frame cavity wall construction? Surely there is an equal risk of thermal bridging here also

Ray Dow

BTW, does anybody know where I could find any drawing details for the this form of construction? head, eaves, ground floor junction etc.

I'm also confused as to what actually constitutes a single skin i.e. is a timber cladded wall considered a single skin even though it has cladding(outer skin), 25mm ventilation void and structural frame (inner skin).

Thanks in advance!

sydthebeat

Ray Dow wrote: »

Any ideas why it's not recommended for timber frame cavity wall construction? Surely there is an equal risk of thermal bridging here also

Who says the additional insulation in the service cavity its not recommended??

Oh, and the place to find details of single skin timber frames is from single skin timber frame manufacturers.

Ray Dow

sydthebeat wrote: »

Who says the additional insulation in the service cavity its not recommended??

Oh, and the place to find details of single skin timber frames is from single skin timber frame manufacturers.

I've been using the Building Construction Handbook, Homebond Timber Frame House Building Manual, Barry's Intro to Construction of Buildings and various websites and none of their details show additional insulation in the cavity.

If you know of any single skin manufacturers that provide decent details please pass on a link, the ones I've checked only have pretty basic ones

sydthebeat

Ray Dow wrote: »

I've been using the Building Construction Handbook, Homebond Timber Frame House Building Manual, Barry's Intro to Construction of Buildings and various websites and none of their details show additional insulation in the cavity.

If you know of any single skin manufacturers that provide decent details please pass on a link, the ones I've checked only have pretty basic ones

when you say timber frame "cavity wall" construction, i take it you mean the standard TF with a block outer leaf.

Here the additional insulation is incorporated in the service cavity to the internal of the frame, for much the same reason as youd use it on the outside. With a cavity wall type TF construction you will not get insulation within the cavity, as the cavity's main purpose is to ventilate away condensate.

with a single skin system the physics are different, and you can have additional insulation to the internal or external, as long as you calculate where the dew point occurs and you design provision to exhaust the condensate away. thats why most single skin systems will have a counter batten system under the cladding to create through ventilation.

as you can imagine the make up of these frames are very specific to the manufacturers, and have design value, so you wont get much more than a basic detail available for free to the public.

while there are systems out there who do specific single skin clad, see griffner haus, most standard TF systems can be augmented to be single skin, once the clacs and the design is done.

why youd want to do such a thing is another question, given the adverse opinions in the insurance market about them.

engineermike

Hi,
I have to agree with Syd - it is an area that need quite a bit of diligence. So much so I have engineers working on 'standard tf' construction that just don't have the expertise or working knowledge of this relatively new construction in Ireland.
Good initial consultancy will pay dividend when choosing & reviewing a system.
If you P/m your details I can point you in the direction of the consultant eng. I use for failure analysis projects on the books at present. The same consultant is utilized by Homebond / Premier to rule out construction detail / systems they do not want to cover.
mike f