Wall vents a moisture concern in Timber Frame?

john_dooley

Hi
I have a Timber Frame House built in the past 5 years. Its not a passive house and I'd imagine just meets the Building Regulations at that time.

After removing some of the internal plastic wall vents, I noticed that the wall vents were installed very crudely.
The OSB looks like it was punched through with a hammer, and there are big holes in the plastic membrane which sits between the OSB and dry wall.
The vents are basically just big holes between internal and external holes.
There was no attempt to seal the membrane or anything.
My understanding is that this plastic membrane is there to prevent excess moisture getting onto the Timber frame (to prevent rot etc).
The (crude) installation of these wall vents would appear to allow mositure to pass out of the internal rooms and into the cavity between the OSB and brick work.

Can anyone offer suggestions on whether this is typical in TF builds, or whether its a concern?

Id have thought there would be a sealed pipe (or something similar) between the internal plastic vent, and the vent on the external brick. And that the plastic membrane would be sealed with duct tape around the pipe.


Thanks

Carlow52

ur analysis is 100% with just one addition:

this (dis)construction detail allows the wind from the outer vent into the frame of the house and it blows out under skirting boards/windowsills fuse board etc: the heat loss is massive.

there are 100's of these houses around, for example all the affordable/social houses in an estate in North County Dublin have this problem.

My solution is the solid duct as u describe with some insulation quality expanded foam to make the seal around the wall vent

john_dooley

Hi
Are there any off-the-shelf sealed ducts I can buy, connecting outer and inner walls.

Or do I have to make up my own , using a plastic pipe + duct tape/expanding foam to seal?

Thanks

john_dooley

Actually, I found an example of what I was looking for.
See "Slimline Wall Kit" at:
http://www.xpelair.co.nz/wawcs0136794/tn-accessories.html

Do some builders in Ireland use ducts like that?
Where can I buy in Ireland (in order to upgrade my house)?

phelangroovy

Timber framed construction is a great Idea...But only that.. .an Idea. I have yet to inspect a timber framed house that was constructed correctly. The cavity should be vented and the plastic membrane intact to prevent the frame absorbing too much moisture. One development I inspected the timber frame was cracking the external wall, the frame was expanding soo much with moisture.

Be careful how you bridge the space between the inner vent and the outer wall. For fire safety the vent pipe should have a fire sleeve to prevent a fire getting into the cavity and spreading through the house!

I expect in a couple of years we will have some dramatic failures which will reduce the value of timber framed.


Guess what! I am not a fan:cool:

Carlow52

Feelingroovy: Nice post
Can you be more specific on what u mean by a fire sleeve and where/how u see the fire coming from into the cavity
Thanks

john_dooley

Hey phelangroovy,
Just so I know what to ask for in the local hardware shop, can you point me towards a link showing the type of pipe you are referring to with the fire sleeve?

Thanks

phelangroovy

If you refer to the Home bond book 6th edition pages 331 & 332 ( will be in the library or Eason (for a free browse!)) yoy will see detail of the fire collar/cavity barrier.