Old houses can be made super energy efficient as well!
Post: April 25th, 2013
Deep Energy Retrofit in Jericho, Vt!
Part 7 - Penetrations, Wood Stove Contintued and Siding!
Dog and girl - Megan (dog) and my daughter Iris (girl) exiting the Southern door.
The 3/4" strapping is visible on top of the air sealing.
Eco Houses of Vermont, LLC
A word first about the strapping.
Firstly, why strapping. In traditional sheathing/wrap/siding
scenarios you just put your siding directly on top of the
sheathing once it is wrapped in Typar or Tyvec (house-wrap).
We aren't doing that for a few reasons.
First off, if you take the time and the money to put an
expensive, super high tech air barrier on the house, you don't
want to riddle it with hundreds of siding nails, each of which
are perforations in your air barrier, nullifying the air
barrierness of it.
Secondly, if you put your siding directly on the sheathing/
house-wrap you are not giving any space for air to circulate
at the surface of the house-wrap to allow for moisture to
dissipate. Yes there is some room behind siding to allow for
evaporation, but we want more air movement.
By placing a 3/4" strapping onto the Mento 1000 air sealing membrane we are addressing both of the above points.
- The nails for the siding are not going directly into the air barrier. They are going into this wood (strapping) which is
tightly attached to the wall. Ken Levinson from 475 High Performance Building Supply assured me that the air barrier
will be fine under these conditions.
To be sure, we are using 7/8" siding nails instead of the usual 1 1/2". With the thickness of the siding this should
keep the nail from going all of the way through the wood and into the air barrier but will have enough hold for the
siding. We tried to get 3/4" nails, but they weren't available.
- As you can see from the picture of the strapping, there are channels between them which allow for air to circulate
from the bottom to the top. Any moisture which gets into the wall can get out and be transported away by either
wind or air being force up by the stack effect, increasing the drying capability of the wall.
Remember we are building a vapor open wall to let moisture that inevitably gets into the walls to get out.
The air barrier we put on the outside of the house has been very carefully selected and applied. The contractor, Jim
Bradley has said on more than one occasion that it is the most detailed work on a house-wrap he has ever done. It would
be a shame to ruin all of that hard work by punching a bunch of holes in it and not air sealing those as well.
Therefore being careful with our air barrier requires we take
stock of all of the bits that we want to stick through our wall,
catalogue them, and ensure that they occur in a way that can be
Here is the list of penetrations through the air barrier on my
- Heat Recovery Ventilation Supply Air Duct (7" round)
- Heat Recovery Ventilation Exhaust Air Duct (7" round)
- Outside Hose Spigot (3/4" round)
- Light over deck (1/2" round)
- GFCI electrical socket on deck (1/2" round)
- Light over front door (1/2" round)
- Light over side door (1/2" round)
- Hole for Air To Air Heat Pump electricity and GFCI socket
- Hole for Air To Air Heat Pump line set (3" round)
- Fresh Air Supply for Wood Stove (3" round)
Ok. There you have it. Ten holes of various sizes. Each with
their own challenges.
Fortunately we have some great tools to help us with these
holes. My friends at 475 High Performance Building Energy
Supply have some great products to help seal these.
Here are two of them. One is for a 6" to 7" tube, like the tube of the HRV. The other is for wires. I used both as well as
one for the 3" fresh air supply for the wood stove. The nice thing about these is that you just put the wire/pipe through it
and either use the attached adhesive pad or use an air sealing tape like Tescon.
Here are a series of pictures of some of the penetrations and how I sealed them.
Wood Stove Fresh Air Supply Penetration
Hole being cut into back of chimney for fresh air supply for wood stove
Hole from outside showing brick, 3" polyiso, 3/4" plywood, 3" poly iso and wrap.
Flex tube fresh air supply coming out of chimney and insulation/wrap.
Filling hole with Roxul rockwool before resealing air barrier.
Repositioning house wrap around hole.
Taping the corners with Tescon tape.
This is what the 3" gasket looks like before it is installed.
Here it is installed but not taped to the wall. See how tight it seals around the pipe.
Taping the gasket to the house wrap using standard
flashing techniques: bottom to top.
Finished gasket taping.
3/4" plywood surround to give the siders something to work with.
Final PVC surround for the pipe. Air sealed and ready for a cap.
Wire Penetration for an outside plug
When you have an outside electrical need, a light or a plug it
goes much easier than these big ones. Smaller hole with a
gasket that is smaller too.
Here I have some extra tape on the air barrier just above
the gasket for the outside plug. This is because my cat, my
lovely cat Freya decided that the air barrier next to the door
on my deck was her new scratching post! Before I could
allow this to be covered with siding I needed to go ahead
and fix this problem.
Damage done to the Mento 1000 intelligent air barrier by my cat Freya. Once
I noticed this damage I put protection up to keep her from making it worse (a
piece of plywood stood up against the wall was enough). This was,
unfortunately not the only place she decided to attack. I used a good 15' of
this expensive tape fixing these transgressions!
The Cat Damage after I had fixed it. Notice the gasket under it. I flashed it
this way to let water run over and down the gasket.
Pics of the Heat Recovery Ventilation Exhaust and Supply Vents
Cutting through the 6" of Polyiso and Homasote "sheathing."
Supply duct hole from inside the mechanicals room.
Supply duct outside. Had to cut the strapping to make it work.
With 6" gasket taped in place.
Here are the 10" screws my contractor got to secure through the 6" of
insulation and into the stud.
PVC surround. The pic is a bit odd. The edges don't look that ragged in real life.
Finished Supply Vent with vent cover.
Both Supply and Exhaust vents finished. They are 6.5' apart to ensure that
the supply air doesn't draw from the exhaust air.
Bring on the siding
Copyright 2013 Eco Houses of Vermont, LLC
Now we just need to get the siding on. I went with vinyl siding. The house had that at the start and we decided to continue
the tradition. It is cheap, goes on easily and isn't heavy. Remember there are 6" of insulation hanging off of the house. If I
added heavy siding it would pull the whole construction down.
Chris West is a Certified Passive House Consultant
Affiliated with the PHIUS and PHI 2013
Insulating the chimney
Since the chimney is outside of the house (who ever thought that was a good idea?) I decided to neutralize the thermal
bridge by wrapping it with Roxul board (R4/inch). With 6" that gives us an R-24 around the chimney. Better than nothing.
The Roxul board for the project cost an additional $770 but was worth it.
Of course after that the air barrier needed to be brought around the chimney as well.
The vinyl siding guys protecting the house wrap from UV rays..
We put the house wrap on in late February. This was the second to
last week of April 2013. The manufacturer says that the Mento 1000
can be exposed for up to 3 months before UV radiation starts to
We got this up after 2 months so we should be fine.
Only thing left to do outside is to protect the EPS between the dirt
and the siding, put the front steps back up and to work on the deck
to get it all set for a summer of use.