Passive House in Austin, Texas

Transcription

1 Passive House in Austin, Texas

2 E Green Group Mission is to : Make Passive House building cost comparable to standard home construction Provide job training to at- risk youth from communities not traditionally associated with

3 Experimentation Time

4 Existing Wall Composite Limestone Gyp board Asbestos insulation Lead Paint and Asbestos texture on all interior walls and ceilings!!!

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7 The house already had a 1700sq ft footprint, which was about what we were looking for our growing family Asbestos removal was going to be $20K for the whole house so leaving it and going with a two wall system was the most cost effective choice. Trees on the lot also made the existing footprint the only practical one. We had the interior asbestos, lead paint, and a portion of the exterior siding for the back bump out professionally removed. The back bump- out made up for any loss of space due to

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9 New wall Composite H A R D I P L A N K ¾ X P S ¾ P I N E Cellulose In a 2x4 Cavity Mini Shelves Made from Landscape fabric used to avoid settling every O S B V A P O R B A R R Filled w fiberglass blown in insulation All Elec. And Plumbing ran through this gap Mini- shelves Fiberglass in a 2x4 cavity Mini shelves 5 / 8 G Y P B O A R D

10 Our benefits from the two wall system - 15/sq ft) It allowed electricians and plumbers to run their pipes/wires with minimal drilling. Eliminated almost all thermal bridging Gave us credit for re- use of existing walls for AEGB Less Asbestos removal required (less airborne particles) than building new Most Affordable PH wall system (no pricey foam required)

11 Draw backs to two wall system Difficult to plumb existing walls without disturbing asbestos. Some inspectors in Austin refused to do partial inspections. Had a lot of termite damage to repair, especially footers.

12 Austin is BAD BAD BAD HVAC contractors = Bad Windows = Bad Sun = Bad ERV = So far, Bad (96% efficient hahahaha!) Humidity = Bad

13 Austin this year Normally 13 days over 100 degrees/yr This year we had over ninety. Ideal for MAX LOAD Ground water temp is between degrees as well. 72 degrees is about 8 feet down. We built the house in winter when it was 18degrees (one of the longest cold streaks in a long time in TX) and the house maintained 65 with a 1500 Btu heater with no insulation, just vapor barrior

14 Specific Space Heat Demand: 3.01 kbtu/(ft²yr) Specific Primary Energy Demand 24.7 kbtu/(ft²yr) Specific Primary Energy Demand (9.3 kbtu/(ft²yr) Heating Load: 3.75 BTU/(ft 2 hr) Specific Useful Cooling Energy Demand: 3.70 kbtu/(ft²yr) Cooling Load: 2.38 BTU/(ft 2 hr)

15 Eliminating thermal bridging Th. Bridge R- 60 Roof R- 54 Walls R

16 Goals! Almost any house, doing a gut rehab, or significant remodel can be made in to a PH with a little bit of thought, attention to detail, and maybe a little flex from homeowners. We use all standard materials that can be purchased at any hardware store We go Low- Tech everywhere we can. Be unremarkable. Houses that fit their neighborhoods, perform the way they should, and are easy to live in. Dynamic in their simplicity. Break the PH stigma

17 High- Tech scares people!

18 HVAC Cooling climate differences to distribute heat and humidity. AEGB requires range hoods and bath fans that vent to the outside. Point source heat expulsion Supplement with a heat pump water heater.

19 What does square footage have to do with sizing an AC system? Your mantra! Our Equipment Fujitsu ¾ Ton mini split Rheem heat pump water heater Recoupaerator ERV

20 Equipment selection Equipment selection Fujitsu ¾ ton Mini- split with heat pump although we are hoping to never use this feature. We used the heat pump model to satisfy the COA requirement for a heating system and to avoid them looking at our actual heating system. Recoupaerator ERV. Still not sure on not working well.

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22 Inline fiberglass windows. We start with the cheapest possible windows that will meet the air infiltration standards and go from there. For my home, the inline 325 series double paned with low E 366 glass was the cheapest (SHGC.19, glazing u.28, frame u.26). SHGC was more important than the frames or glazing. Going triple pane brought us down by.04 of a kbtu

23 Rheem Heat pump water heater Drawbacks : very tall, makes noise, needs 1000 cubic feet of space to draw from. We put it in a very small closet with a louvered door above the ERV and put a return for the ERV in the closet so it would be constantly circulating the cooler exhaust air to the rest of the house, as well as exhaust the rooms. Also connected a small hydronic heat exchanger from the water heater to the supply of the ERV from the water heater. So we will be heating the water (which cools the house, but then using that to heat the house. The heat pump water heater is actually a hybrid, it switches over to

24 Winter ERV

25 Recent developments : i.e. notes from Kat has given up on the idea of a central cooling unit that can be distributed through the house by the ERV because of latent load Orleans. On point expulsion makes a big difference. So does multiple de- humidification devices

26 Summer Scenerrio? Closed Loop ERV

27 Pace House Affordability Study

28 Their goal was $120 to $140/ sq ft My goal is always $100/ sq ft. Plans showed a 2400 sq ft house with three car garage We are at $93.00 / sq ft ($223,300 total including $44,640 O+P) before finish, $126/ sq ft ($302, 277 including $60,445 profit) after finish This is the same price that we can build a code building for.

29 Cost analysis Bjornstein Fleenburg $12, $16, $45, $ 302,277.00

30 Pace House Not using 2 wall system. They have 2x6 wall Also have specified some higher end finish materials putting them over $100/ sq ft. Recycled mesquite flooring, quartz countertops, Ipe siding, local white brick, high grade metal siding, etc.

31 Pace house cost breakdown Our climate only calls for double paned windows with low SHGC. When the client tried to go away from PH by using aluminum doors and windows that were leaky, the cost actually went up. HVAC tripled or quadrupled, Windows stayed the same or went up Insulation went down, but it was cheap. When you are confident in your ability to meet the.6ach50 you can stop charging more to meet that standard.

32 Evans house

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