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| "Things are going great, and they're only getting better" |
Richmond is great, and there might be no better time of year to live in old Fist City than sweet sweltering Summer - so long as you can handle the suffocatingly warm embrace of Humidity. In preparation the Augusta Project has recently donned a pair of shades, and while my suggestion of a tasteful tortoise-shell finish was unwisely disregarded for a more trendy louvered shade (Kanye wears those, right? Yes. So zeitgeisty, this house.), the shades should do a decent job of keeping the summer sun off of those big kitchen windows while still allowing plenty of light through.
Specifically, we designed the louvered overhangs to provide shade across the entire window assembly at noon for the 15 days on either side of the summer solstice on June 21. The shades also get some help in the mornings from fairly large and leafy neighborhood trees. By designing to these constraints we allow the winter sun (which tracks at a lower angle) to provide some passive heat gains at the kitchen and master bath.
-ETM
Thanks for reading. We'd love to hear comments, questions or suggestions either in the comments section or you can email us at blog@rmichaelcross.com
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Between holidays, deathblizzards and work, winter 2010 has been a busy but beautiful one here at R Michael Cross Design Group. Much has happened at Augusta Ave. since our last post in... November?!? Oh man.... Well, I think I'd like to break it down into a few not-so-chronological parts.
The main developments in the construction process have been:
- the installation of plumbing work
- the installation of electrical work
- roofing & siding
- insulation
Big strong men are slinging up sheets of drywall and bellowing epic Soviet marches AS I TYPE THESE VERY WORDS. Fact.
Okay, let's get down to brass tacks:
Electrical
While very important, addressing sustainability within the electrical scope of the house is fairly straightforward. You want to specify efficient fixtures and appliances, and you want to develop methods of switching, storage, and organization that prevent unnecessary electricity usage- "vampire power" or "phantom load" if you will. Tribble Electric and Ferguson were integral in helping design, develop and specify an electrical system. At the end of the day, your efficient fixtures won't help much if your actual lighting layout is inefficient. This is the sort of value that professional designers provide moreso than in-depth technical expertise.
Plumbing
Efficient plumbing has a little more method to it. Again, you want to select efficient fixtures and water related appliances. Kohler and Ferguson were very helpful to that end. In an earlier post we discussed the collection of rainwater for good old fashioned all natural American toilet flushin', but we haven't discussed the "structured plumbing" method for conserving potable tap water.
As you probably know, almost everyone who isn't a wartime sailor turns on the faucet or shower and waits for the water to warm up before washing. This is inefficient. In a structured plumbing system the goal is to reduce the distance between the faucet and hot water supply to less than 10'-0" by using a hot water loop with a remote activated recirculating pump. It's simpler than it sounds. The end result is that- instead of opening up the faucet and pouring half a gallon of water into the sewer- you press a button to activate the pump, then open the faucet to near-instant hot water. Waste is reduced to under 2 cups max.
Roofing & SidingIt's great to finally see the house with most of its clothes on. The roof is constructed primarily of recycled rubber shingles, with one flat section of high albedo TPO adhered to half an inch or so of insulation, and a sloped high albedo metal roof at the sunroom. We chose unfinished Nichiha fibercement siding as an affordable high quality alternative to Hardie siding. John Gray at Peak 3 Construction gave us our mitered corners. All is well.
InsulationHonestly, the change from uninsulated to insulated house was possibly the biggest experiential change so far, besides the change from pile of sticks to framed house. I mean I walked into the house (empty that day) and immediately thought "I sure could take a nice mid-afternoon nap here right about now." Kind of weird, I know, and probably correlative to other things beyond my immediate environment, but if you know me really well, you know it isn't really something I'm good at, this napping. It's not that I dislike it- quite the contrary actually- I'm just no good at it. A useless napper.
We used Weatherseal to develop an insulation solution that fit both our insulation needs and our budget. We ended up with this pretty intricate solution involving three different types of insulation:
- 2x6 wall cavities filled with spray cellulose
- Existing exterior brick walls sprayed with 1 1/2" of soy based closed cell spray foam (Demilec HEATLOK Soy)
- Roof rafters filled with soy based open cell spray foam (Demilec SEALECTION Agribalance)
Using cellulose in the new exterior walls took advantage of our use of Dow SIS panels and allowed us to focus our resources on providing some sort insulation and sealing on the brick walls, and just insulating the living daylights out of the roof (couldn't be helped). The cellulose has the added benefit of being made of old papers and absorbing sound like crazy. Additionally we've also sealed all of the doors, windows, sill plates, king plates, etc. with low expansion spray foam or silicon caulk as appropriate.
On the design end we've been feverishly selecting, deselecting, and reselecting sustainable finishes and working out relevant details. This should all come to fruition rather quickly in the coming weeks, so please stay tuned for updates (I promise!)
For now, here's a gallery of the latest.
Thanks for reading. We'd love to hear comments, questions or suggestions either in the comments section or you can email us at blog@rmichaelcross.com
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Things are moving along at 4600 Augusta Ave: all of the windows and doors are in, and we’re quickly approaching the time to insulate. Pinning down the best method for insulation has been a surprisingly difficult process… while building science reports have increasingly advocated tight full-home conditioned envelopes using unvented roofs and conditioned attics, we’ve found contractors to be generally skeptical of the spray-foam technique, citing the lack of ventilation along the sheathing as cause for concern about shingle temperature and degradation. Shingle manufacturers themselves have expressed confidence in their products in the assembly; however, given the degree/prevalence of contractor pushback we decided to throw this one over to the R&D department here at R. Michael Cross | Design Group, and enlisted the invaluable help of Guy DuBois of Commonwealth Building Sciences for a sort of case study to examine the effect of underside ventilation (or lack thereof) on roof surface temperature.
To break this down a little, I should explain that vented attics were mandated by code for years as a means of preventing roof damage resulting from trapped moisture. In this method, insulation gets put down between the second floor ceiling joists, vents are installed in the eaves and gable ends, and the attic is left essentially unconditioned. There are a few main thoughts behind the original mandate: preventing the buildup of moisture during the colder months by allowing it to escape, and preventing ice damming at the eaves in the winter by keeping the entire roof cold. Dominion Power further explains:
At some point, the original purpose for attic ventilation was forgotten and/or replaced, in cooling climates, with the belief that it was to reduce roof and attic temperatures, thus lowering cooling expenses and increasing shingle life. This was further compounded by the leap of faith that increased or powered ventilation would be even better. While sounding logical, there is simply no research to validate it. In fact, scientific testing has shown that attic ventilation has almost no effect on roof surface/ shingle temperatures and very little effect on attic temperatures.
While Dominion’s research would seem to answer our question… we decided to move forward anyway. Because we’re scientists, dammit, and we need some of that good empirical stuff.
The key to unvented roof assemblies and conditioned attics is managing the temperature of the first condensing surface either with rigid insulation on top of the sheathing, or with an impermeable barrier of spray foam insulation adhered directly to the underside of the sheathing. In the case of rigid insulation, this keeps the condensing surface at the roof sheathing sufficiently warm (45°F) to minimize or prevent condensation. In the case of applied spray-foam, this moves the condensing surface from outside of the insulation (the roof sheathing) to the inside of the spray-foam, which is essentially self-insulated by the rest of the foam behind it.
This method of keeping the condensing surface below significant insulation also allows the exterior roof surface to remain relatively cool, preventing ice dams. Furthermore, the absence of direct attic ventilation helps minimize uplift pressure in high wind events.
To study the surface temperature performance of unvented roof assemblies compared to unvented roof assemblies, we constructed two 2’-0” x 4’-0” mockup sections of roof, one with two inches of spray-foam applied directly to the sheathing, one without.
From there we set the roof panels up at a 12:12 slope and set up matching heat lamps (250 watts). Guy spent some time calibrating the whole set-up, making certain both panels received equal heat exposure. After heating both panels for about 15 minutes, the heating lamps were turned off and initial surface temperature readings were taken.
We found that both panels had a surface temperature within 1°F of 181°F. We chose to continue measuring at intervals over the next half hour to see if the panels rejected surface heat at the same rate.
Ultimately, the panels performed almost identically, with the unvented panel cooling slightly slower, presumably because of the foam’s thermal mass. Measurements taken behind the panel showed an expected but marked difference in hot spots, with the insulated panel performing significantly better.
We admit that this investigation could have been more controlled, and that the panels may not exactly reflect the performance of an actual enclosed roof assembly; however this was a helpful exercise in essentially pointing towards a confirmation that unvented roofs won’t melt your shingles off. At the end of the day, we believe the positives of an unvented spray-foam assembly present a better solution for residential roofs in most situations.
We wish we had somewhat more conclusive results, and may still pursue further tests on these panels. In fact, we’d love to hear any of your suggestions and ideas for testing methods, or even general questions that you don’t think we have addressed. You can also email us at blog@rmichaelcross.com.
| ETM
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