Here are a few specifications that help reduce energy consumption and achieve lower impact on the environment:
* All electric loads are minimized to reduce consumption. Appliances, lighting and all electric equipment are sourced to minimize power required. For example, an induction range/oven is sourced for kitchen.
* Super insulated, double stud walls: the cavity between the studs are filled with 15" of Roxul mineral wood insulation for an R60 wall. A rim board [and it's associated thermal bridging] has been eliminated by the use of a balloon framing technique. All the roof and floor loads are carried by the interior stud wall.
* Super-insulated roof: the roof have 6" of polyisocyanurate insulating board that is covered in a 2 ply torch on modified bitumous membrane [typical on commericial flat roofs]. There is a further 14" of Roxul batt insulation in between the roof I-joists creating an R70 roof.
* High thermal mass with 2" concrete topping on the main and 2nd floor. This thermal mass will help reduce the temperature swings inside by storing thermal energy in the concrete.
* 4" of rigid insulation under concrete basement slab. This is to reduce heat loss through the concrete to the earth.
* Large triple glazed, fibreglass-framed windows with films that allow passive solar gain on the south and a different film to help insulate further on the east, west and north sides. There are only 2 windows on the north side of the house. Passive solar heat gain is expected to provide about 30 to 40% of the heat required for the house. The fibreglass frames have a similar co-efficient of expansion and contraction as glass, so the the seals between the glass and the frame, theoretically, should have better longevity.
* Natural ventilation through operable windows, placed in rooms for cross-breezes to help air flow.
* A stair tower with windows at the top and bottom to encourage "stack effect" for natural ventilation.
* Use of only electric systems- no gas line was installed. One energy source for heating and power was sourced in order to avoid additional "connection fees, transmission fees, riders, etc." that would have been the case with gas. Electric connection to the power grid also allows for a PV system to provide surplus power to the grid. Even though electric heat is created by coal power plants, the heating energy that will be required is relatively low, so that it is a not a large carbon creating source.
* Low flow water fixtures [toilets, aerators, faucets, etc.] and with a grey water system roughed in for future, possible rainwater use for toilet flushing.
* Selection of low volatile organic compound [VOC] or off-gassing materials. Also, use of re-used materials [lighting, doors, etc.]
* More to be listed as installation occurs!
Hi,
ReplyDeleteFirst off - thank you! I have been following your blog for several months now and very much appreciate your candor and willingness to share in every tiny detail of this construction. I am learning a lot!
I believe you mentioned in a previous blog that you are holding off on the PV installation until a later date. Is this in part to get an accurate read on the homes consumption before sizing up the requirements for generation? Also, have you installed 'stand-offs' of any kind for a future PV installation down the road or is the plan to cut into the membrane and attach to the structure later? Thanks,
David
Hello David,
ReplyDeleteThanks for following the blog.
We are roughing in the PV and at this point, we're likely to install a 4 kW system to provide a sunshade/awning on the south windows. Ultimately, we will want to produce about 10 kW on site. The 10 kW number is based on our Hot2000 energy model, in terms of what we will likely need to heat and power the home, as well as talking to Peter at Habitat Studio & Workshop, who has some good data on energy consumption for "netzero" homes. I also expect the prices for PV to drop considerably in the next 5 to 10 years, as production becomes more competitive, so I am hedging the investment.
Furthermore, we have installed blocking in the wood exterior wall to carry the PV structure/rack system.
ReplyDeleteOn the roof, we are providing a built-up platform that penetrates the roof membrane which will be sealed. This work will happen right away.
Shafraaz, As a former photographer, I love the lighting in the latest picture. The house looks great.
ReplyDeleteThanks for posting all of this info. It rounds out previous postings. The latest information also prompted some questions.
Could you give some more details about the wall assembly? Is the internal wall 2 x 6? Is the balloon framing continuous from the foundation to the roof? Is the exterior wall also 2 x 6? Did you have to install fire blocking in between the two wall assemblies? Are you installing a vapour barrier, and where will it be in the various wall planes?
Is the information about the roof's R value correct? My understanding is that PolyIso performs at about R6.5 per inch. 6 inches would be R39. Roxul is about R4 per inch, so 14 inches would be R56. The total is R95. Am I overestimating?
In the paragraph about the triple glazed windows, your train of thought skipped in the sentence about passive solar gain. Could you amend this.
Thanks - Jim.
I just went back to the November postings. I noticed the outer wall is not continuous, but appears to be one wall stood on top of another. How did you tie the outer and inner walls together for structural strength?
ReplyDeleteDid you have to add any other bracing to support this assembly? - Jim
Hello Jim,
ReplyDeleteTo answer your questions:
** Is the exterior and internal wall 2 x 6?
No, both are 2x4.
** Is the balloon framing continuous from the foundation to the roof?
No. As you've noticed, we stacked one floor on top of another.
** Did you have to install fire blocking in between the two wall assemblies?
We are using Roxul mineral wood between interior and exterior stud walls.
** Are you installing a vapour barrier, and where will it be in the various wall planes?
Yes, the poly VB will be on the interior stud wall.
** Is the information about the roof's R value correct? My understanding is that PolyIso performs at about R6.5 per inch. 6 inches would be R39. Roxul is about R4 per inch, so 14 inches would be R56. The total is R95. Am I overestimating?
I always account for a decrease in R value due to the wood I-Joists that also share this space. For that 14" depth, there is a wood I-joist every 16 inches on centre. This brings down the R-value. I may have under-estimated, but I'd rather be conservative.
** I noticed the outer wall is not continuous, but appears to be one wall stood on top of another. How did you tie the outer and inner walls together for structural strength?
Did you have to add any other bracing to support this assembly?
The interior and exterior 2x4 walls are tied together by two layers of 3/4" plywood plates. The outside OSB will help also to tie the floors/studs together.
Thanks for the answers. -Jim
ReplyDeleteI am interested in fire blocking within the walls because, when I freelanced as a photojournalist, I had to cover quite a few fires. I spoke to several firemen about how fire behaves in structures and I read about the experiences of residents who had narrow escapes. I hope the following will not freak you out.
ReplyDeleteSeveral lessons stand out. A balloon framed wall acts as a chimney. Fire blocks between levels stop the heat from rising, reducing/slowing the advancement of fire and smoke. In your case, Roxul is noncombustible, so that would impede fire spread. The 3/4 inch plates which connect the inner and outer walls would be a form of fire block.
Another lesson is the use of doors at the top or bottom of stairs. This also slows the spread of fire and smoke. You mentioned you will have an open stair well. This concept will help distribute the heat throughout the house, but in a fire, it will also be a chimney.
A couple of years ago, I read about a fire in a brand new house. The house was designed with an open concept downstairs with cathedral ceilings. The bedrooms were located in a loft overlooking the living room. An electrical short circuit ignited the Christmas tree. The homeowner said that when the smoke alarm started to wail, he exited the bedroom. He was met by a wall of smoke which was rising from the lower level. The family barely escaped. The man said his next house would have two separate floors with doors in the stairwell and a secondary, easily-accessible escape route from the upper floor.
Hello Jim,
ReplyDeleteThanks for the lessons learned!
Here are my thoughts:
1. I am hoping the Roxul packed in between the studs will be a bit of a fire retarder. I can imagine why it may travel quickly in a typical, lightly insulated building.
2. There the plywood plates are actually 1.5" thick [2 layers of 3/4"]
3. Yes, the open stair is a natural chimney. Part of our strategy was to use steel and LVLs for stairs and railings [non-combustible materials].
4. All our bedrooms are on the ground floor. This is so we can living with the view in our waking hours! And also results in a safer, more faster exit directly to the ground floor.
5. That said, I think we'll look into investing in a rope ladder for emergency purposes from the loft and upper floors!
Thanks again for your insights!
I cannot remember where I saw them, but there are kits of rope or chain ladders which can be rolled and stored in a box under the emergency exit window. The ladder is anchored inside the box. When the ladder is dropped out the window, there are built-in standoffs which hold the rungs away from the wall. This allows room for your toes similar to the space under kitchen cabinets.
ReplyDelete