OSB on the inside & Uber-Airtight
Pedro…
look your OSB is on the inside
Check out this video.
http://www.youtube.com/watch?v=MgfgazrrSlw
These guys are building Uber-Airtight and Uber-Insulated
They are using OSB on the INSIDE as the primary AIR Barrier and virtually no foam.
The Video is about a prefab project .. but the layering and the Use of tape and gaskets instead of foam is very fascinating and could be adapted to stick built construction.
Notice the Red and Green Tape… AIRSTOP TAPE
How many years will TAPE last?
We depend on sealants and foam Already…
How long will they last?
Why not tape???
The roof construction is stick by stick…
The process is very interesting.
Very thin Sheathing(perhaps with a waxy coating) goes on top of the rafters..then tape then furring ….and then I could imagine radiant barrier decking for my climate…. and then business as usual (choose your own roof cladding)
This would be a cold roof for winter and a radiant barrier(cool roof) for summer.
Look at the attention to detail and the Blower door results at the end !
Replies
Hi homedesign,
look your OSB is on the inside
You nailed it.....but....it only addressed air infiltration.......I didn't see anything about thermal bridging.......so top marks to their air sealing.
I like the idea of tape, foam and/or caulk where applicable. I wonder how long their tape will stick?
I'd still wrap it in polyiso foam panels before the siding.
I also found it interesting that they also OSB'd the ceiling.....my idea has the OSB on top but it does make sense in dealing with air infiltration.....you and I've gotta think on this some more.....what'cha thinkin'?
Pedro the Mule - Thanks for the link!
I did OSB on my interior for my bedroom remodel, I will continue as I go around the house. I thought about doing the ceiling too, but I couldn't think of a really good reason to do so.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
I thought about doing the ceiling too, but I couldn't think of a really good reason to do so.
Didn't you see the Chevy Chase "vacation" movie where he fell through the ceiling plaster while watching movies in the attic? View Image"...everyone needs to sit on a rock, listen to the surf, and feel the ocean breeze in their face once in awhile."
cambriadays.com
Pedro,
They have addressed the thermal bridge..
look at around 2:32 ...
http://www.youtube.com/watch?v=MgfgazrrSlw
there is a thermal break between the rafter and the "sub-rafter"
here is a video that shows wall construction... major thermal break in the wall
http://www.youtube.com/watch?v=PDfhwFwYozE&feature=related
Edited 6/22/2009 11:45 am by homedesign
They have addressed the thermal bridge..
look at around 2:32 ...
http://www.youtube.com/watch?v=MgfgazrrSlw
there is a thermal break between the rafter and the "sub-rafter"
Wow homedesign...you've got a quicker, clearer, more observant eye than I.
Yep, I see it now....that's a pretty awesome way to do that....gets extra insulation depth "&" thermal break.....the first couple of times through I thought that was some sort of OSB rafter I beam but the osb is actually the roof deck above...duh
Gonna have to sit down this evening and start scratching my head on some new thoughts for this. It sure does a lot for resolving moisture issues with todays designs. Sure used a lot of lumber but the offset is lasting quality and long term energy efficiency to make up for the environmental impact on lumber.
Is that rockwool they're using?
Pedro the Mule - Now ya done gone and done it....me head won't stop wobbling around
Is that rockwool they're using?
Pedro,
It looks to be some type of mineral wool
Dan at JLC thinks it might be something like this
http://www.rockwool.us/sw34066.asp
Looks like Roxul brand rockwool. Nice stuff.... great for sound proofing beside fire resistance and insulation qualities.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Could you explain the blower door results? Me no speeka blowa dowa!
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Paul... i do not spreckenzee myself
I do know that these are Passivhaus projects... so they are at least better than 0.6 ACH at 50 pascals
I think(not sure) the gauge is reading 0.44 ach50 on this project
I speak a little blower door. ASHRAE Standard 62-1999 calls for 0.35 air changes per hour, with no less than 0.15. Not familiar with that manometer - lot fancier than mine, I am guessing it reported a 0.44 ( it was labeled N50 on their display, which I am assuming is the same as ACH50).ACH50 is calculated using the CFM50 blower (ft3 /min at 50 pascal), the volume and an "n" factor".CFM50 really doesn't mean much without the volume of the house.More confused ?
hmj ...
I was just guessing that they had already entered the Volume of the house into the "gadget"... just guessing
You do realize that anything under 0.6 ach50 would translate to an exretemely low number of air changes Natural ..
I think that reporting air changes at 50p is a better metric...
you do not need to guess at an "n-factor"
Edited 6/22/2009 12:42 pm by homedesign
The "target exchange rate" we give is 35%. Almost any house I see, older than a few years, is at least 60%, which we consider leaky.Where are you getting 60% from?
HMJ
I am quoting the passivhaus standard
60% of one airchange per hour at 50pascals
sometimes shorthand will be written as 0.6 ACH 50
this is VERY tight compared to existing homes!
When you do a blower door test depressurized at 50 pascals
The reading will be in CFM ..
(my house was 386 cfm at 50 pascals)
Convert cfm to cubic feet per hour and divide by the house volume to get the
Air Changes per hour at 50 pascals.
No need for n-factor
Edited 6/22/2009 1:09 pm by homedesign
homedesign,ya got a link to the passive house standards? We go off BPI protocol, tweeked for our state MD.The N factor is based on the number of stories. I seem to recall reading where/why/how it was developed - maybe in Home Energy Mag?
Hmj,
The measurements that you are familiar with are the most common.
Airtightness is usually reported in estimated NATURAL Air Changes per hour.
Passivhaus and some others who are striving for more Airtightness are starting to report in Actual Air Changes measured when the house is de/pressurized to 50 pascals.
Building America among others is reporting air changes at 50.
Here is a link to Passivhaus
http://www.passivhaustagung.de/Passive_House_E/airtightness_06.html
Here is a link to a definition of Passivhaus from GBA
http://www.greenbuildingadvisor.com/glossary/8#letterp
Natural Air changes per hour is entirely an estimate ..based on climate,number of stories and wind exposure
Numbers can range from 1/10 of ACH50 to 1/30 of ACH50
In reality natural Air Changes can be almost zero sometimes and greater than 1/10 x ACH50 sometimes
I can't imagine that the estimating method is very accurate - maybe on a small, square, single story on a slab...
I can't imagine that the estimating method is very accurate - maybe on a small, square, single story on a slab...
Hmj,
For comparing "Airtightness" and setting minimum standards:
Reporting Air Changes measured "at 50" is much more useful than Estimating "Air Changes Natural"
The proposed 2011 Energy Star standard for measuring infiltration will be in units of(ACH50)
http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/2011_Proposed_National_Program_Requirements.pdf
Edited 7/13/2009 9:29 am by homedesign