straw-bale deep energy retrofit

Straw-bale home construction has been around for some time, but this project, done by Keith Warren, owner/operator of Straw Wrapped Homes, is a made-in-Alberta approach to using straw bales for a deep energy retrofit. In 2017, Keith used his technique on a 1963 Bungalow, and has lived in the home since 2020.

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Drayton Valley, Alberta

Keith Warren developed this process himself (he owns the patents) for attaching straw bales to the exterior of a home in a way that allows the air to flow through the straw. This prevents condensation and protects the straw bales from the elements. What's more, straw is a locally available by-product of agriculture, and sequesters more greenhouse gasses than is required to plant, harvest and store. Warren's system adds an R value of 40 to the building in addition to what it already has. Since 2020, the home's 8.5 Kwh solar has provided all the energy requirements of the building, which is completely electrical. The home is tied to the grid, but generates more power than what is purchased during overcast days and extreme temperatures in the summer and winter.


BEFORE

AFteR

ENERGY 
CONSUMPTION
BEFORE
GJ/year
AFTER
GJ/year
COMFORT
BEFORE
Frequent temperature swings
AFTER
Limited temperature swing in both heating and cooling seasons, significant reduction of exterior sounds
BUILDING CONDITION
BEFORE
1963 bungalow, structurally sound,Needed new roof, windows and Electrical (100 amp) and plumbing
AFTER
New metal raised rib roof, triple glazed windows throughout, electrical upgraded to 200 amp, no natural gas, new plumbing throughout, new insulation, new drywall, new woodwork - cabinets, doors and door frames wheelchair accessible, barrier free master bathroom, new flooring
RENEWABLES
BEFORE
None
AFTER
8.5 KWH solar panels on roof, metal raised rib roof allows solar panels to be attached without roof penetration. EV Charging station in new double garage.
WAll Insulation
BEFORE
R8 fiberglass, no vapour barrier. Twenty-minute fire burn rating.
AFTER
R12 fiberglass, 6 mil vapour barrier, R40 exterior straw wrap, building paper and new stucco. 2-hour fire burn rating.
Ceiling Insulation
BEFORE
R15 (estimate), wood shavings
AFTER
R60 fiberglass extends across the top of the straw bale insulation column, 6 mil vapour barrier.
Foundation Insulation
BEFORE
2x4 framing with 1/4" paneling
AFTER
R40 straw wrap/ 8" above grade, R20 fiberglass interior walls to footings/floor joists R40 fiberglass/ 6 mil vapour barrier to footings
Windows
BEFORE
Aluminum sliders
AFTER
Triple glazed, triple low E coating, double Argon gas fill between panes, PVC frames. All windows are recessed on the exterior to reduce wind effect on the surface
Ventilation
BEFORE
None
AFTER
Broan 7.1 HEPA (Heat recovery ventilation system) With 70’ of 4” plastic pipe below grade in the crawl space to pre-heat incoming fresh air (air intake -30C temperature is +7 C at the HRV intake/Summer temperature +25C is reduced to +15C at HRV intake supporting air cooling.
Heating
BEFORE
1980 gas furnace
AFTER
Individual room thermostatic controlled- electric base board heaters, sized for individual room heat loss.
Cooling
BEFORE
None
AFTER
No mechanical cooling system required because of the superior insulation envelope.
Hot Water
BEFORE
1980 pilot lit gas fired hot water tank
AFTER
Standard 40-gallon electric hot water tank which utilizes room air temperature to raise the incoming water temperature from +3C to +15C. All sinks in home have 'on demand' electric heaters for source point hot water.
Download Case Study File
About Straw Wrapped Homes

Straw Wrapped Homes provides a model for rejuvenating existing architecture from a 50 year to a 100 year life span incorporating net-zero energy efficiency, multi-generational living spaces with barrier-free access. The use of straw bales for superior insulation eliminates green house gas emissions associated with standard insulation materials. Keith Warren has been designing and building energy-efficient double wall homes since 1982.

Off the Wall Construction and Renovations Inc

Keith Warren/keithcwarren4@gmail.com

780.542.9404