Actual Performance
Last Post 06 Dec 2017 08:13 PM by whirnot. 8 Replies.
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whirnotUser is Offline
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04 Dec 2017 12:25 AM
So there have always been a ton of ideas, and technical information on this forum. But in the end you have to find the "sweet Spot" between cost, efficiency, Sustainability, and Architecture. This of course varies greatly by Locale. I don't recall ever seeing any results. I would be interested in seeing examples. Our Home: 2300 Sq Ft, 3 BR, attached two car garage (insulated) Insulated slab on grade Walls R27 Ceiling R60 Alpen 725 on South side, rest Alpen 925 Two Minisplits, One fireplace (three cords per year) Hardie siding, Standing seam metal roof. Total cost including Electric service and ATT wastewater treatment system $123.00 PSF Area: Primarily Heating ( approx. 7000 HDD) Used Cooling one day. All electric, including well pump and pumps for ATT Included. Garden irrigation included. Total Electrical use for one year: 7381 KWH Total electrical Cost: $488.00
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05 Dec 2017 11:48 PM
Not bad at all!

And when rooftop PV hits $1.50/watt all-in you could even take it to Net Zero without robbing any banks, if so inclined!
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06 Dec 2017 01:07 AM
Net zero would be great, but as for now doesn't pencil out.
Then there is the matter of utility return as our utility pays back on a cost avoided basis. Which I interpret as wholesale.
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06 Dec 2017 03:27 AM
So obviously we could have spent more and increased performance but it appears that the return will rapidly diminish. I would really be interested in hearing results of other projects if folks have them to share.
greentreeUser is Offline
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06 Dec 2017 01:27 PM
Probably need more information to make your results meaningful. What level of foundation insulation,wall makeup, blower door result, 1 or 2 story, if 2 story how many sf on main level. Did you have it built or did you act as gc. What temp do you keep your house at in the winter, in the summer, do you overheat with the fireplace to let it coast, was is designed to be passive solar, ect.
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06 Dec 2017 06:13 PM
Located in Central Oregon, dry climate with large Diurnal swings, often 40 to 50 degrees. Average low temp below freezing 7 months of the year.

2300 sq ft Slab On grade. attached 24x24 garage on Northeast corner
One story, basically 40 x 60 rectangle oriented due east and west. Actually over 60 but steps down twice in width. Contemporary design

5" slab over R10 XPS (would have preferred EPS but concrete man was afraid of cracking when walked on. I know, but you gotta do...) Exposed Concrete cut on 4 foot centers. No cracks. One room covered by Bamboo, 1 Cork.
Foundation insulated R10 outside to footer, inside r5 perimeter. Foundation insulation stops 1 inch below wall to allow wall insulation to bridge joint between wall and footer. Taped.

Wall stack: 5/8 sheetrock, 2x6 Advanced framing except double top plate. Dense packed Cellulose, 7/16 Osb, House wrap, 1 inch polyiso, with every seam taped. Hardie siding, some lap, some sheet and batten.
Critical joint wall to floor: Sill seal, Ply edge from behind sheathing lapping over Foundation, to protect sheathing from concrete and cover joint. Bottom plate caulked with silicone to foundation Metal flashing from behind siding to below grade.

Cantilevered trusses, multi hip design. 42 inch overhang on south side, remainder 24"
Blown in cellulose including r60 over HRV ducts.
Very expensive Standing seam roof $32000 + Total roof area over 4000Sq Ft.

Alpen 725 windows on south side for increased solar gain average U.15. All other windows Alpen 925. U.11 or .12 54% OF WINDOWS ON SOUTH

Two minisplits, Mitsubishi Hyperheat. Great room-18000 BTU Strictly backup to fireplace, only used when out of town. Second in master suite 9000 BTU usually set at 65.
Fireplace Focus 320, rated at 10 to 30K BTU (initial Manual J called for 18000 BTU. total to maintain)
Lifebreath HRV Configured to move air from Bathrooms and 1 bedroom, returning to great room where most heat is generated. HRV used as needed to maintain approx. 45 to 50% RH in summer and 40 to 45% in winter.
We did not do a blower door test. If I stopped sheetrock after ceiling was hung, it would have resulted in a several week delay to get them back.

Marathon electric water heater with 85 gallon tempering tank. All appliances Energy star. Heat pump clothes dryer. 100% LED lighting
Designed for passive solar and approved for Oregon Passive solar tax credit. 3d modeling resulted in no sun hitting windows in summer, doesn't even hit south wall in July.

We keep it about 70 to 72 in winter and about 68 to 71 in summer. Warmest it ever got in summer was 73. Open windows at night to cool rooms and slab, hold temp all day
In winter, a small fire in the morning maintains till solar exposure takes over, on cloudy days low fire in maintained. in evening we build a fire when temp drops below 69 then stack a good fire when going to bed.
If one gets up during the night we add a log.
House rarely varies more than 2 to 3 degrees room to room.

I was the GC.
The most comfortable house we have ever lived in.
greentreeUser is Offline
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06 Dec 2017 07:21 PM
Good post. How is the temp variation in the other 2 bedrooms. Do they just get residual heat off the other 2 mini's?
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06 Dec 2017 08:12 PM
They are within a couple of degrees. Residual and the hrv draws warm air to them when its on. We try to use the hrv only during the day.
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06 Dec 2017 08:13 PM
They are within a couple of degrees. Residual and the hrv draws warm air to them when its on. We try to use the hrv only during the day.
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