Bishop Passive House: Exterior Insulation Pt 1

The purpose of exterior insulation/the reason  we're using exterior insulation on a house   like this. The benefits of exterior insulation are  really like two or three fold sometimes four fold.   So one: We're keeping the cold out.  We're putting our jacket on the outside,   but in this instance we're also using this to  keep the heat out. So I think we've shown in other   videos or in other photos that our walls here-our  exterior walls- heat up to above 130 degrees even   in the coolest temperatures here in the winter  time just from the from the sun hitting them.   We've used our laser thermometer to test that  even with our walls, the exterior of our walls,   hitting 130-132 degrees, the inside of our  sheathing (which is only you know 40 millimeters   of insulation and then half inch of plywood  sheathing so it's only about two inches away)   is still maintaining the same ambient temperature  that the rest of the building is. So we don't have   windows in yet so our interior sheathing will be  just the same as the outdoor temperature, but we   know that we're keeping about 50 degrees worth  of heat out of our wall cavity just from having   40 millimeters worth of wood fiber insulation  on the exterior of our walls. On that note,   we've found that there's this thing  called the psychometric chart and   it's really important for builders (building  scientists know about it) but it's really good   for builders to learn about it as well and to  study it and know the purpose of it the graphs   the x and the y axis because it tells us when our  walls have a danger for mildew growth and then   mold growth after that. We've learned um Jennifer  Rennick and I from Inbalance have learned that   if we have say 70 degrees inside the house  and it's 50 relative humidity which is   pretty much what most of the Central  Coast would be especially at night   and then we have only 50 degrees outside  in that same time period which is actually   warmer than it is on an average night here it's  you know last night it was down in the low 40s   and it was in the 30s just a few months ago.  So if we have just that 20 degree difference   between our indoor and our outdoor temperatures  with the 50 relative humidity inside the house   you can look at that chart and that tells  you that you have a danger of condensation   occurring as the warm air with 50 relative  humidity hits the inside of your sheathing.  Hey there. Let's talk about the psychometric  chart. On the bottom of the graph   is temperature and on the right side is moisture  and those curvy lines are relative humidity.   So in the situation that Mike is talking about  it might be 70 degrees and 50 relative humidity   inside the house. No problem. You find that on  your psychometric chart. But then overnight the   temperature drops to like 50 degrees. No problem  outside, but what happens is that the sheathing   is also 50 degrees so the inside air is getting  into the wall cavity and then it has that same   amount of moisture but when we see it in the  psychometric chart now we're at saturation.   So that's when we might get condensation on the  inside of the wall and potential mildew growth.   That's one of the reasons why we really like  to have an exterior insulation because that   keeps the wall cavity from not getting quite  so cold and having the issues of condensation.  There are so many benefits. Sound  attenuation. That's probably the biggest one.   We've got two close neighbors who are awesome  neighbors. Two people from Boston. They have a   pretty large garden and a very busy gardening  crew out there every other day. So lots of   weed whackers, lots of gas powered leaf blowers.  There's construction happening on the house across   the street. We're anticipating that house being  lifted and the third story going up so there's   probably a year or two worth of construction  that's going to happen across the street.   We have a small car collection next door  that likes to be revved up every morning.   Oh and we also have really high winds.  This house is in kind of a wind zone   so this 40 millimeter inch and a half  of insulation is basically going to give   them like kind of like noise cancellation. It's  like noise cancellation headphones for a house.

Channel: Cairn Collaborative

Views: 458

Rating: 4.8000002 out of 5

Keywords: construction, passive house, education, building, sustainable design

Id: ww1y5mwsuu4

Length: 4min 50sec (290 seconds)

Published: Wed Aug 25 2021