Affordable Cold Climate
homedesign
| Posted in Energy Efficiency and Durability on
Does any one care to “Challenge” Building America?
http://www.buildingscience.com/documents/case-studies/cs-ma-westford-hfh
Is there a “greener” and user friendly way to provide
An Affordable 3 bedoom 2 bath Home for a Cold Climate?
Optional Hint … the 2nd floor can be re-arranged
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1. Even though the site appears heavily wooded, there must be sunshine hitting one of those walls in the heating season. Therefore, I'm disappointed not to see larger windows with a high SHGC on that wall. In other words, they ignored their passive solar opportunity, which is zero cost.
2. I find the floorplans to be very efficient, with generous bedroom sizes. I'd love to hear more about your 2nd floor idea, though. The second floor doesn't have a space-wasting hallway, which I really like.
3. In a smallish superinsulated home like this, a ducted gas forced air furnace is highly inappropriate. (It's first cost is excessive and you can't "zone") They call it "right sized" but I haven't seen any central furnaces small enough to be right sized for this house. Maybe the mfrs. are starting to make them. Anyone seen a 16,000 btuh central furnace?
4. They also ignored Solar DHW, which I guarantee is cost effective if the cost can be held to under $3k. It can, but that's another thread - Simple Solar.
5. The cost of solar PV continues to drop, so they should have included some low cost features that will simplify its future installation.
It's not a bad house.
I'm a little confused about why there are two ventilation systems -- a central-fan-integrated supply ventilation system, as well as an ERV. One system would work; why install both?
If the budget permitted, the next upgrade would be to triple-glazed windows with orientation-specific glazing.
Entirely too foamy...
You all know how I feel about the hermetic house. But, aside from that and the excessive mechanical system, I would have made it a 1-3/4 storey house and eliminated the dormers. The small additional cost of materials would be more then offset by the decrease in fussy construction details and potential leak points. And it would have created more usable storage space, perhaps eliminating the need for a basement.
Great care and attention was taken to seal and insulate the house. However, without a main entry airlock, every time the front door is opened, the heat will escape.
Jim,
Studies have shown that the heat loss associated with opening and closing entry doors is relatively minor, and the added cost of a two-door entry cannot be justified by anticipated energy savings.
Nevertheless, a mudroom is nice.
More likely, the dog will escape. Airlock entries are vestiges of the 80s when houses were sufficiently leaky that it made a difference.
Just like a thermal envelope air barrier can be anywhere in the system - because convection requires an entry and an exit - in a super-tight house, air can't "escape" unless replacement air can enter. Of course, with the door open, the R-value of the entry has reduced to zero and there will be short-term heat loss, but this is true with an airlock as well unless the airlock is not conditioned space.
The more important function for an entry, particularly in a small house, is as a mudroom - a place to take off snowy or muddy boots and wet coats, hang them up, store outdoorsy stuff, brush the dog, etc. It can also double as a laundry and/or utility room (all the mechanicals should fit in a closet).
The tiny entry hall in this design is hardly functional as a primary entry for a house full of kids. The smaller the house, the more important become storage spaces and accessory rooms like mud/laundry/utility rooms. And the traffic flow is straight through the kitchen work area. Poor space planning in my book.
for all the insulation, the heating loads didn't come down very much. is it really a 1.5 story 1,340 sf house if there is a daylit, functional basement?
-axe casements if going for airtightness
-exterior images on p. 4 show fair amount of sunlight - why the horrendously low 0.28SHGC?
-dining room is essentially unusable for a long rectangular or square table.
-no airlock needed for balanced ventilation system
When I said "greener" I was thinking Less foam.
My thought was similar to Robert's.
Except instead of 1-3/4 story .. go full 2 story with laundy & generous storage on the 2nd floor and eliminate the Basement.
With a Flat Ceiling and vented attic to take advantage of what John Straube calls...
"The lowest-cost, highest performance roof system."
It is better to avoid bedrooms above/near Master Bedrooms.
The 2 upstairs bedrooms could move to the front.
It's an unfinished basement with cellar slider windows that don't meet minimum fenestration guidelines for living space.
It has double-hungs, not casements.
Actually, it looks like the house is heavily shaded.
There's enough room for a 4'x8' table with chairs.
An airlock has nothing to do with a balanced or unbalanced ventilation system.
I'm not defending the design or details, but you seem to have missed the mark on every point.
John,
Where'd you find that chart?
robert,
thanks for the oversight, i meant double hung and not casement.
on page 4, the bottom right picture shows the facade completely lit by sun.
you can fit the table, but you won't be able to get by on both sides.
way to fight the good fight, robert.
link to Straube's paper with chart
http://www.buildingscience.com/documents/reports/rr-1006-ba-high-r-roofs-case-study-analysis/view?searchterm=1006
Mike,
As is plain to see in the first picture, this is a heavily wooded site with the trees very close and surrounding the house - clearly not a site for passive solar design.
In some cases, window style has to be consistent with the overall aesthetic. In this design, casements would have been inappropriate.
A small house, of course, doesn't need more than a 42" x 64" dining table, but even with a larger table, there's plenty of room for chairs and traffic because the dining room is open to the living room.
Just trying to keep the critique reasonable, accurate and constructive.
Am I reading that chart right? Seems there is virtually no difference in the predicted heating usage in a R-13 vs R26 wall and a R-13 and a R-40 roof. Why would they even model an R-13 roof? If this chart is correct, seems like a lot of foam for not much benefit.
Do they not need a termite inspection gap up that way?
I think it is a fairly efficient design and looks pretty good for a Habitat house. A few nitpicky things:
- They spent a lot of time managing the details to control water - why not go ahead and do one of the simplier things to control water - install gutters
- I think the dormers look a little odd being a full two stories - I would have continued the roof across the front with a little "rain table" to make it look like a real dormer.
- Getting really picky but a pet peeve of mine - no shutters on twin windows.
Purely decorative, non-functional shutters are ridiculous in any case. To continue the eave line across the shed dormers would have dramatically reduced the window size (has to be large enough for egress), gutters are a maintenance nightmare so close to deciduous trees and with snow and ice sliding off a steep roof, and you're not reading the "parametric study" bar graph correctly.
Those are all incremental improvements over the base case. The +13 and +26 are the addition of 2" or 4" of polyiso on to the base wall or roof. And each does make an incremental reduction in heating load - all adding up to the goal of -44.1%.
Robert,
Thanks for your rational approach to this discussion -- much appreciated. I agree with most of your points.
Even though I understand your point about the style of the house, I would have chosen casement windows -- and the glazing would have had a higher SHGC on the south side, even if the sunlight is filtered or partial.
But thanks again for defending some of the decisions made by BSC on this house. No house is perfect, but this is a nice house for Habitat.
I have great respect for BSC/Building America and I think this house is a very good example.
I think the home is attractive and the floor plan is very well done.
The question that keeps crossing my mind ....
Is the "Build it Out to the Roof Rafter" strategy the most "buildable" and affordable design concept for Super Insulated homes?
My personal home design is based on the BSC "out to the rafters" strategy.
My home was not extremely costly and it performs very well.
I would NOT call my home affordable and it is not superinsulated.
The HERS index on my home was 51
Moving toward 2030 we need to do better than HERS 50
I am looking for affordable, durable and buildable strategies.
I thought the floor plan was very unimaginative, and I agree with Mike that an 8' dining room does not work. Good design does not need to be sacrificed for energy efficiency.
If you want to quible about the size of the dining room.
It is not only 8 ft wide since it shares space with another room.
All the rooms in this home are small by some standards.
Not too small for a yacht or a luxury motor home.
John
Too small for a table with chairs on both sides. Now if the wall was removed between dining and family room it might work better. As a spec (and custom) builder I am always sensitive to design. By the way John, I am in a seminar now at IBS called Seeing Beyond the Glare of "EcoBling" with Architect Peter Pfeiffer from Austin.
I admit to knowing little about basements or building in Cold Climates.
just wondering.......
If Basements are not "mandatory" ....
Why have a basement in a small AFFORDABLE home?
If 2nd floors are not mandatory.......
why have a 2nd floor?
basements and 2nd floors =
challenging or impossible for aging in place
Why build $stairways$ as big as a kitchen?
Who will clean/paint the high gutter, siding and soffit?
A one story is more user friendly for sweat equity construction crews.
Why not more square feet of a cheap highly rated Roof System?
I know there will be more foundation footprint with a 1-story
But it must be much cheaper than Basement footage?
The conventional wisdom in cold climates for basements (since we stopped hand-digging them) has been "if you need to go down 4' for a crawlspace foundation, why not just dig another 4' and throw in a basement? The marginal costs are very low per square foot, definitely less than building the second floor. Historically, however, unfinished basement square footage is not allowed in the multiple listing service database.
H4H is the Denver area even takes some criticism because they usually choose volunteer safety over basements. No one can get hurt by accidentally falling into a crawlspace foundation. For the same reason, they have eschewed the second floor until recently as vacant land has become scarcer.
My cost analyses, however, are showing me that a frost-protected monolithic slab is more cost-effective than a basement as long as the land is cheap. Once the price of land reaches about $20/sq. ft., then a basement is required by the homebuying market.
Five inch gutters and downspouts coupled with pop rivets will provide more reliable and lower maintenance gutters. That's another one of those things that spec builders don't care about since they won't be around to maintain things.
I think this has mostly to do with tradition. In a cold climate, footings are at the bottom of a frost wall so it makes sense to just go a few feet deeper and make it a basement.
FPSF design makes energy efficient slab on grade an option.
I think the FPSF approach is not very well understood by many "conventional" builders - and there is resistance to change.
One thing you have to say, BSC is putting it out there---the information, the studies, the floorplans, the knowledge, the analyses, etc. Their site is an awesome resource.
John Brooks - Hopefully this response is not a hijack of your original question. BSC does have a four-square design for cold-climates. Note that the overall building envelope / size is very similar to the Westford house (since it doesn't include a basement). It gives you the boxy architecture and efficient thermal design (where you can pile on the insulation in the vented attic). What it doesn't give you is the rectangular shape that would best take advantage of passive solar heat gain (well that, and the symmetrical windows). See it here:
http://www.buildingscience.com/documents/case-studies/cs-il-prairie-crossing-four-square/view?searchterm=four+square
But I do have a challenge. The BSC designs OFTEN use foam---SPF, XPS, or polyiso. I understand their reasoning, and the cold sheathing argument, but their high R-value case studies argue against some of the statements on this forum.
Compare these two links:
http://www.buildingscience.com/documents/information-sheets/high-r-value-wall-assemblies/high-r-wall-05-truss-wall-construction/?searchterm=high r-value
http://www.buildingscience.com/documents/information-sheets/high-r-value-wall-assemblies/high-r-wall-02-advanced-frame-wall-construction?topic=doctypes/enclosures-that-work/etw-high-r-value-enclosure-assemblie
With statements like this:
"When it comes to high-R walls, the most cost-effective option in most areas is a double 2x4 wall with a total thickness of about 12 inches, insulated with dense-packed cellulose," writes GBA senior editor Martin Holladay.
"I've built or designed nearly every permutation of double-wall house and none is as quick, easy, effective or resource-efficient as the modified Larsen Truss." Robert Riversong
"When it comes to high-R walls, the most cost-effective option in most areas is a double 2x4 wall with a total thickness of about 12 inches, insulated with dense-packed cellulose." Martin Holladay
"A double-stud wall filled with cellulose can perform very well, as long as:
1. You address concerns over moisture accumulation in the exterior sheathing by using plywood or boards, not OSB, and by including a rainscreen between the sheathing and the siding, and
2. You pay close attention to air sealing on the interior (by following the Airtight Drywall Approach).
As long as you follow these details, you're all set. And it should be the least expensive wall.
That said, foam-sheathed walls perform very, very well -- and they do a better job of addressing thermal bridging at rim joists. I love walls with thick exterior foam sheathing. Their two major drawbacks are:
1. They usually cost more than double-stud walls, and
2. There are increasing environmental concerns about rigid foam products (questionable fire retardant chemicals and a very long payback for some blowing agents in terms of global-warming potential)."
Martin Holladay, in response to a Q&A question on double-stud walls.
For cold climates, it seems to me that there are definitely risks with each approach---the "foamy and not-so-foamy" (if I can borrow John's description).
• Foam - Decreased drying potential
• Not-So-Foamy - Moisture accumulation in the cold sheathing
Both can work; both have risks. So why does BSC give the truss-wall a rating of 15, and the foam sheathed wall a rating of 20? Is this prejudice or science? The BSC case study shows that double-stud walls and truss-walls are more expensive, less durable.
Are there really double-stud or truss-wall houses out there---built in the '70s or '80s---that are failing because of moisture issues?
We're all aware of the EIFS failures, the unintended consequence (or lack of understanding) in the early days of foam-sheathed walls. What about thick cellulose walls?
I just know that I'm beating a dead horse, but there's still too much controversy here . . .
John - I agree on the basement issue. Basements were often built as root cellars. In those cases, the high moisture environment and uninsulated walls worked well. ;)
I too wonder about the 1st floor / 2nd floor argument. Any case studies out there on cost efficiency? Seems that price per square foot would be lower with a 2nd floor design---because you're distributing the foundation and roof area. I'm interested in further information on this point.
I'm not so sure about the slab-on-grade. Why not a sealed and insulated crawlspace, if only to allow flexibility in the future? There are ways to reduce footing depth to a reasonable limit, to avoid a 4' high crawlspace. PVC pipes buried in concrete? It bothers me . . .
I think if we decide to build with less foam.....
We should Rethink the AFFORDABLE Strategies.
Vaulted Ceilings, Conditioned attics and 1-1/2 story Designs demand Roof Systems that are more Costly, more Risky and Not-So-User Friendly
Daniel,
But isn't this kind of attention to detail important to any high-performance project?
A truss wall can put 2/3 or more of the R value outside of the rim joist without trouble... Is this "advantage" of foam over-rated?
What about the Saskatchewan conservation house? I think it's still occupied...
https://www.greenbuildingadvisor.com/blogs/dept/musings/forgotten-pioneers-energy-efficiency
http://www.greenland-innovation.com/Artek-Lowenergy/Tuesday/Sisimiutplus1(Dumont).pdf
Edited for spellin
Two reasons: in New England, basements are traditional (and that means also conventional), and the smaller the home the more that people (think they) need a storage space for "stuff".
Again, it's partly local vernacular architecture, partly the cost of land vs cost of building.
But I agree completely on the stairway the size of a kitchen problem. In a small cape-style house, it's quite possible to design a straight staircase (I've done it in a 24' wide cape) which uses half the space of a U-shaped stair.
Though it wasn't a cold-weather house, HFH set the world's record in 2002 in Alabama for building a one-storey house, complete with sod and landscaping, in 3½ hours.
The tipping point in favor of slab-on-grade over crawlspace is that the slab can be the finished floor. Stained concrete is still trendy, bulletproof, and saves at least $3/sq.ft. on your floor system.
My concrete floor is six years old, had zero maintenance*, and looks just like the day we moved in.
The thermal mass and the way it buffers the temperature is just a bonus.
It also has advantages over modular construction. No one is shipping floor-less modules for structural reasons, so modular won't let you save the money and enjoy the durability of a slab.
You are right in that the biggest drawback is the lack of easy remodeling.
*Cleaning is not maintenance.
I think you're right on the money here John (22). I would think that a safe, efficient, home that is easy to maintain would be a dream come true to those in need of affordable housing. Function over form or form for function. Never form over function as is the case with many large custom homes.
In coastal and flood prone area's building without a basement is the norm and seems to work fine,
I see no reason or need to include a basement with this sort of home.
Strawbale infilled into a pole barn style frame without alot of frills, using earthen plasters is still the champion as far as I'm concerned. The open interior space created by the this type of frame allows for just about any type of interior layout. I have been tweeking the numbers for building homes this way and truely addressing the percieved concerns. Have not seen a better, more cost effective or safe proposal yet. The advantages far outweigh the reasoning behind the concerns.
There is no resolving the basements-versus-slabs debate. Southerners love their slabs, and most Southerners don't seem to mind ducts in their attics. Northerners love their basements, and can't understand why Southerners wouldn't like them too.
Basements are relatively cheap to build (compared to 4-ft. frost walls), provide lots of storage space, provide a place to put the furnace and water heater, make it easy to modify plumbing -- and, oh yes -- also provide a place to run ducts within the home's conditioned space.
Martin,
I knew you were a "Basementist"
In Texas we cherish the Garage.
At least some of the Affordable Housing around here is doing away with the Garage.
But you guys don't want to give up your basements.
You go 8' deep here you either hit oil or water.
John,
Basements are way more useful than garages. Garages freeze; basements don't. You can't store a bucket of drywall mud in a garage.
I usually keep my bucket of drywall mud at my off-site climate controlled warehouse.
Some low-foam cold climate details by Harold Orr, NRC vintage 1982.
Only one full basement.
In New England, a basement was originally a root cellar, had to be dug by hand, and was typically lined with field stones. It also contained the "footing" for the central chimney.
When central heat came into the equation, a deep cellar was necessary for the humungous coal burner and the "octopus" of ductwork to the first floor rooms, with a huge cast iron return air grill in the middle of the floor. And that had to be space in the cellar for coal storage, typically with a chute from outside at grade to fill the bin.
If it was a rural house fed from a spring, it often had a cistern in the cellar. After rural electrification (which happened in the memory of living people in this area), cellars contained well pumps and pressure tanks, and knob-and-tube wiring and cast iron and steel plumbing in addition to the ductwork of the now-converted-to-fuel oil furnaces.
Still cellars were typically dank, dark places with dirt floors and dry-laid stone walls. But post-war generations were built of modern cinder block with perhaps a rat slab and a sump pump to evacuate the water that leaked in the Spring thaw or after a heavy rain - and they became places to store the increasing amount of consumer goods that families began to acquire.
If the basements were dry enough - perhaps because they were made of poured concrete rather than block - a part would get converted to a "rec room" and eventually people came to expect a basement that could be finished into extra living space - which led to the relatively recent conditioned basement.
But some old time New England builders still say that to build a basement is like building a swimming pool and trying to keep the water out. And, now that we know the environmental costs of concrete and that shallow foundations are possible in cold country, full basements are making less sense. But, absent a full basement, a well-designed house must include plenty of storage spaces - indoor and out - for "stuff", though a 2-car garage can take up some of the slack.
If you have neither a garage nor a basement, where's the mud?
I have to bring all my leftover latex caulks, paints, glues and mud into my overcrowded mudroom (where else would "mud" go?).
I pile it on the floor next to and behind the woodstove. But a bucket of mud ended up drying out on one side - the side facing the woodstove. So it's either frozen or cooked. Now I keep only Durabond over the winter.
Isn't the rimboard a "foam sandwich" -- spf on the inside, polyiso on the exterior? With the exterior polyiso , there shouldn't be a need for the spf in the joist bays, as it's not done on the 2nd floor bays.
"But you guys don't want to give up your basements." --where are you supposed to store wine?
The problem with storage space
The more Space ....the more "Stuff"
Less space = Less Stuff
Maybe We should not encourage Hoarding.
Have you seen the video of Dan Morrison's Basement?
My detached one car garage is almost full of stuff now.
Time to build a new shed.
edit to say oops.... it was Dan's Garage/Worshop
Robert - thanks for explanation on the chart - makes sense to me now. I was actually looking at the other "dormer" on the other side (bottom of page 4) but I guess couldn't do that on the stairwell side - although you do not need that for egrees.
I have seen many foundation failures due to lack of gutters. On a story and half construction cleaning gutters periodically is easier (and more likely to happen) than bringing in soil to keep positive drainage away from the house from the erosion from the uncontrolled runoff. Can't say I an familiar with snow and ise issues so can't comment on that - may be a location thing and our clay soil may contribute as well (NC).
Martin and Robert,
Thank you for responses #6 and 7. I've lived in a cold climate all my life. None of the homes have been airtight, so I do not have any experience with airtight homes without airlocks. However, I have felt the cold winter's blast whenever the door was opened in a leaky house. It's a pet peeve, but when I can finally build my passive solar home, I'll include the airlock in the main entrance. I will also include a mudroom airlock for boots, and drywall mud, if needed. The cost may be an unnecessary expense, but we all have our personal list of needs, wants and luxuries.
Enjoying and learning alot from your discusions. I'm a T.O. renovator in the planning stages of a house that will be R2000/Passsivhaus. Looking for more builders info on techniques though. Any N American sources.
T.O. renovator?
Unfortunately, even with all the details provided by BSC, it is impossible to compare this building's energy performance to another in any meaningful way. The only information provided is the floor area -- either 1408 SF or 1340 SF -- and the total projected annual electrical and gas usage. Using the Passive House methodology of calculating source energy, I get 350 kWh/m2a. That is almost three times higher than the Passive House standard allows. I wonder if the projected energy use includes the window A/C visible in the photo on the BSC website: http://www.buildingscienceconsulting.com/portfolio/westford-habitat-house.aspx
Is there any information on the heating and cooling load for the house? It's hard to answer the original question without that information.
"Is there a "greener" and user friendly way to provide An Affordable 3 bedoom 2 bath Home for a Cold Climate?" The simple answer is Yes: multi-family housing that is close to public transportation.
Bottom line: cold climates ain't affordable. Thank the Goddess for Global Warming.
T.O. is short for Toronto. sorry. Especially info on envelope
there are few projects under development in Toronto right now:
http://passivehousetoronto.blogspot.com/
http://torontonetzerohouse.blogspot.com/
Adrian