Silicone as air tightness seal

just do it

Tonight's "about the house" featured a house using a silicon seal for air tightness as a substitute for tape. Is this a credible alternative? I've my doubts...

MicktheMan

I somehow doubt that silicon would last the useful life of the house even if it is sandwiched between timber/osb. I'm no expert on silicon or its constituents and so am open to be convinced.
I also noted that the actual airtightness result was not given, hhhmmmmm

sas

Yeah, everyone is skeptical about that particular approach. It may well give excellent results up front. It may continue to do so for years to come. The only thing it appears to offer over the specialist tapes etc is price.

If the silicone starts to degrade down the line then you're in bother and any savings vs the tapes will be quickly eroded.

just do it

MicktheMan wrote: »

I also noted that the actual airtightness result was not given, hhhmmmmm

Yes I noted that too!

just do it

A google of silicone seal life expectancy throws up results of 5-20 years, harldy inspiring. It would be nice to have an airtight home for life, not just for 5 years!

JuniorB

Should this thread not be in the Animals and Pets section?
I hear that's where all the Passive House design guys hang out these days!

BryanF

JuniorB wrote: »

Should this thread not be in the Animals and Pets section?
I hear that's where all the Passive House design guys hang out these days!

can you elaborate, thanks?

muffler

JuniorB wrote: »

Should this thread not be in the Animals and Pets section?
I hear that's where all the Passive House design guys hang out these days!

Warning given. We can do without those type of comments.

Do-more

just do it wrote: »

A google of silicone seal life expectancy throws up results of 5-20 years, harldy inspiring. It would be nice to have an airtight home for life, not just for 5 years!

The other side of the coin is the question of whether the anticipated service life of air tightness tapes are to be believed?

Are they all tested in conjunction with the substrates they are used on?

Take OSB for example it's not a nice even substrate to start with so can you be sure that you have a perfect bond along every inch of tape? And is there anything in the OSB (or any other substrate) that might migrate over time and break down the bond?

60 years is a long time....

JuniorB

BryanF wrote: »

can you elaborate, thanks?

My post was in reference to the house builder featured in the show who happened to be a vet and was very proud of the fact that he had designed his passive house with apparently no professional input what so ever. :cool:

Sorry if any offence was taken... none intended!

DOCARCH

JuniorB wrote: »

My post was in reference to the house builder featured in the show who happened to be a vet and was very proud of the fact that he had designed his passive house with apparently no professional input what so ever.

Ahh....subtle! See where you're coming from now.

Just to add I too would be somewhat skeptical about the use of silicon to seal the joints in the timber frame and the fact they were promoting that it could any old silicon (not some form of certified silicon for the purpose).

Either revolutionary or a big (long term) mistake!

just do it

I for one have to say I'm disappointed with the "about the house" programme last night. My trust in Duncan has dropped dramatically. At least with Kevin McCloud if he sees something he doesn't think is right he highlights it immediately. Duncan last night I feel has mislead the public and set back the cause of passive house by showing what should properly be classified as a highly energy efficient house as a passive house. He just about said enough to cover himself without fully highlighting the deficiencies of the building system from a passive house perspective.

I don't believe he ever referenced the Passiv Haus Institute, PPHP or passive house certification. Surely as the standard setter he should be promoting the highest of standards. As an example the use of silicon as an alternative flies in the face of the following video from the NSAI website, which ironically is an extract from an earlier "about the house".
- NSAI Agrément Airtightness & Insulation video

just do it

Find tuesday night's programme here. Chat on airtightness starts at 4:45. Now with the TV cameras rolling you'd expect exacting detail of silicon application, but at 5:54 a good inch gap is left in one such strip!

Having said all this I think the system possibly has some merit and is worthy of further investigation, but for a start I'd include Agrement certified tapes.

tred

Its crazy really. Whats he actually saving in cost. He has zero come back in 6 years time, if the silicone degrades. He has some with the highly tested
certifiied air tightness products out there.

beyondpassive

MicktheMan wrote: »

I also noted that the actual airtightness result was not given, hhhmmmmm

Interim airtighness result was under 0.5 ach with a large gap still to be filled.

L driver

just do it wrote: »

I for one have to say I'm disappointed with the "about the house" programme last night. My trust in Duncan has dropped dramatically. At least with Kevin McCloud if he sees something he doesn't think is right he highlights it immediately. Duncan last night I feel has mislead the public and set back the cause of passive house by showing what should properly be classified as a highly energy efficient house as a passive house. He just about said enough to cover himself without fully highlighting the deficiencies of the building system from a passive house perspective.

I don't believe he ever referenced the Passiv Haus Institute, PPHP or passive house certification. Surely as the standard setter he should be promoting the highest of standards. As an example the use of silicon as an alternative flies in the face of the following video from the NSAI website, which ironically is an extract from an earlier "about the house".
- NSAI Agrément Airtightness & Insulation video

Hi,
Both these guys are architects with a handy tv number, and both seem to know sfa about energy efficiency etc. So neither are standard setters imo, and I would have liked if they had let Viking House talk for longer as they are building these houses for years.

just do it

beyondpassive wrote: »

Interim airtighness result was under 0.5 ach with a large gap still to be filled.

Well that is good to hear, and I'm glad for the homeowners.

What would be interesting is to see the results of airtightness testing over a number of years, not only of this house, but of houses of varying building types using a variety of airtightness strategies. Who's to say that airtightness tapes will live up to the 60yr cert from NSAI?

For example how long are airtightness tapes in existence? As passive houses have been built on the continent for at least 1 or 2 decades it would be interesting to know how they are now performing.

just do it

So is the saving worth the risk?
Using certified tapes and an experienced airtightness team would at a guestimate cost €4-5,000 extra. Given the extension is 2,500 sq ft this is a cost of €2 per sq ft.

Should airtightness fail dramatically in 5-10 years what would be consquential cost of overcoming this - both capital cost and annual cost (if a form of extra heating most be used)?

Hardly worth the risk in my humble opinion.

just do it

On a standard build, silicones might be used to seal this junction, but these would only work for a while and would eventually break down over time with the expansion and contraction of materials, whereas an airtightness tape such as XXXXXX will accommodate that.

Was reading about the Denby Dale PH and came across this line which reminded me of this thread from a while back....

tred

Did the big man duncan who knows it all ,not question the use of silicon!...anyway, its too la now.....!!!!