Tuesday Morning Session
Notes by Dana Rubin, Account Executive for Green Energy Times
Overwhelmed by the possibilities of this conference, I take the plunge and slip into my first workshop.
Building an Airtight House:
Now, sitting in with the Center for EcoTechnology, a group of 20 are learning about ways to keep houses air-tight.
We desire:
1. comfort in our homes and
2. durability
BUT air infiltration combined with thick fibrous insulation can cause serious durability issues.
Question: How effective is dry wall?
A: Air cannot flow through dry wall.
Passive house technique, sheet rock layer — use as the interior air barrier, use more permeable layers as added overlays.
Vapor barriers used to stop amount of water that moves through a wall assembly: approx. ⅓ quart of water diffusion via humidity.
** The tighter the house, better the humidity levels are maintained within the house.
Air leakage issues: Where is air leakage really coming from?
- Radon, soil gases. (You want to reduce this)
- connections to a garage, car exhaust, carbon monoxide
- attic dust
In leaky houses, the above locations are where we see the most amount of leaks. Locations where air infiltration is coming from,
Quick solutions: seal the cracks.
Long term solutions: need new membranes – completely sealed, corner to corner.
Home Energy Magazine. Is that house an air filter?
** The leakier the house, the greater the risk for outdoor pollution .
The House is A SYSTEM:
- Air Sealing
- Insulation
- Heating and Cooling
Building Enclosures:
- WATER: control water flow – first function of building enclosure. Examples: House Wrap, Siding, Drainage Pipes, Layer against concrete — control the flow of water.
- THERMAL: control thermal flow — that’s your insulation —
- AIR: control air flow
- VAPOR:
Identify in your building — which materials are providing one of these 4 functions, creating full loops.
“Thermal Barrier”
Insulation should be continuous. Heat will flow the most where the insulation value is the least. Don’t have cold air by-pass the insulation. The fiber-glass should be touching the drywall, you do not want space between the assembly. Don’t have your drywall be your air-barrier. Have a high R-value
Use spray foam to prevent condensation on the dry wall. Closed- Cell Foam.
Air Control — where inside and outside air separate. Controls the flow of air through the building assembly to be effective:
Continuous
Strong
Durable
Stiff
Air Impermeable
Primary Air -Barrier: Every gap, seam and connection is VERY TIGHT– then you could have additional air barriers.
Vapor Control: controls the diffusion of water through the assembly reduces drying potential want to use the most permeable vapor control later as we can while still preventing condensation. It is preferred to use a semi-permeable layer. This is the one layer that can not be redundant, needs to be a single layer. Need a primary vapor control.
Class I Vapor Barrier: impermeable
Polyethylene, sheet metal, foil facing
Class II Vapor Retarder semi-impermeable
kraft paper facing, extruded polystyrene
Class III Vapor Retarder” semi-permeable
Plywood, OSB, latex paint.
Class IV- don’t provide vapor control
housewrap, unpainted drywall
Interested in seeing more workshops, I sneak away from Center for EcoTechnologies and head over to The Master’s Guide to Designing Spray Foam Insulation:
Remember: Continuous installation !
Thermal Bridges: When there is a gap between materials and structural surfaces. Conduct better than the foam they are supporting,
Why don’t we use the passive house standard for our first line of defense?
Return on investment?
air barriers: gypsum wall board,
Deep Energy Retofit
