http://www.thefreelibrary.com/Passive+Houses%3A+what+may+happen+when+energy+efficiency+becomes+the...-a0295268301

As with any new technology, the problem is not the technology itself but a lack of understanding on the part of the designers and the installers. A knowledge of both psychrometrics and properties of materials is essential.

I have been specifying earth pipe systems successfully for 4 years, for both commercial and domestic projects in lieu of air conditioning. The pipes must be laid to fall to a sump and a pump used to remove the condensate, as there will be condensation in the matrix during summer when used for cooling. The pipes must be made of a conductive non-absorbent material which does not support microbial growth.

This requires a piping system manufactured from solid (not foamed as standard) polypropylene and impregnated with silver to prevent microbial growth. Hence the expense of properly designed systems.

Within the commissioning procedures the underground matrix has to be cleaned of all dust using pressure washing and pressure tested to ensure there are no groundwater leaks.

Posted By: djhThe OSB issue seems more of a concern to me.

It's a concern for me too. I am not using OSB as a vapour barrier, I have a plastic sheet VB and then a 70mm insulated service cavity inside of it. I was however considering to use a layer of OSB or shuttering ply then plasterboard on two of the kitchen walls and two of the living room walls to aid the installation of kitchen units, shelves etc.

As such I would be looking to use the cheapest product available which will get the job done but in doing so I don't want to endanger indoor air quality due to formaldehyde emissions.

Thoughts anyone?

[Edit] It seems there is a EN classification system for formaldehyde emissions with the best classification being E1 which is negligible to zero emissions.

Thanks David, the plasterboard is already on site so I will probably end up with getting OSB if the local stockists have low formaldehyde stuff. A quick look on the net shows them listing two products Class 3 Contifinish and Class 3 Nexfor, no idea if the classification is for emissions or something else or what the difference is between contifinish and nexfor but I will quiz them when I am in the store next week. Failing that the fermacell will be the next option.

The report by Leeds Metropolitan University, (leedsmet.ac.uk) identified other probable causes of the problem - at least as important as the non-draining earth tube. The insulated timber frame had a brick skin separated from the frame by a 25cm unventilated gap. The bricks got saturated by the rain. It is proposed that in summer sun on the brickwork would raise the temperature of the bricks to way above that of the timber frame and interior so raising the relative humidity of the cavity and wood frame assembly to 100% (and thus above dewpoint). With little capacity for moisture to evaporate either externally or internally disaster struck. An earth tube that wasn't ventilating and formaldehyde release certainly wouldn't help the internal atmosphere but a properly functioning one would not have overcome the wall problem. One message might be "beware internal vapour excluding layers unless you are sure you know where water vapour/water is going" or put another way "Long live ventilation and evaporation".

djh, I think it's the one in this thread...

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=8240

yes, definitely mm!

I think it was leedsmet.ac.uk/as/cebe/projects/tap/tap-part1.pdf

bella - I'm getting '404 Page not found' for that link of yours.

Ah well. bella's 'link' took me to the Leeds Metropolitan site but the 404 error came up on the site. Did try going through the various site links on there, but I was chasing my tail.

Posted By: djhI've just come across an interesting article.

http://www.greenbuildingadvisor.com/blogs/dept/musings/belgian-passivhaus-rendered-uninhabitable-bad-indoor-air" rel="nofollow" >http://www.greenbuildingadvisor.com/blogs/dept/musings/belgian-passivhaus-rendered-uninhabitable-bad-indoor-air

It concerns a Passivhaus that apparently was declared uninhabitable because of problems with the ground tube used in the ventilation system, and with the OSB vapour barrier.

Lots of food for thought!http:///forum114/extensions/Vanillacons/smilies/standard/shocked.gif" alt="" title="" >

If anybody finds a copy of the original paper that is mentioned, I'd appreciate a link or a copy.

That's an interesting article, particularly to me as I am in the process of internally insulating solid brick walls with EPS and an OSB inner sheath (starting from outside 220mm brick, ventilation gap, 100-150mm EPS, 18mm OSB sheathing).

Having read that I am going to be extra careful that the ventilation gap is properly vented top and bottom!