A random click on a random YouTube Video sent me down a rabbit hole on Passive Houses. The short explanation of the Passive House concept is to significantly reduce the energy needed to maintain desirable conditions inside a structure using advanced building technology. The concept or origin of Passive Houses is from Germany.
One of the items used in the YouTube Video that caught my attention was the use of tape to secure and ensure the Water Restrictive Layer and Air Barrier Layer is sealed.(1) Of the, I don't know how many, videos I have watched of building various structures I did not recall the use of taping to seal these layers prior to finishing. Another interesting difference I noticed in the YouTube Video was the use of a Service Cavity.
Building Techniques Used:
- Highly insulated building envelope (2)
- High performance triple glazed windows (2)
- Elimination of thermal bridges (2)
- Continuous air sealed layer (2)
- Heat recovery ventilation (2)
Highly Insulated Building Envelope - 5 Sections
The Building Envelope includes the walls, roof, floor, windows, and doors.
Water Shedding Layer (1)
This layer is the outer most layer and its primary function is to prevent water from entering the building structure.Water Restrictive Layer (1)
This layer is directly behind the Water Shedding Layer. The Water Restrictive Layer's job is to restrict the amount of water able to gain access to the structures behind it. Conventional construction uses tar paper; in the YouTube Video (1) that caused the rabbit hole dive into the topic they use a particle board type of material.
Insulation Layer (1)
The Insulation Layer is the layer that has the buildings insulation in it and in the Passive House design mentioned in the YouTube this means 2 inch by 10 inch lumber on the exterior walls (1).
Air Barrier Layer (1)
The Air Barrier Layer prevents heat loss or gain through the movement of air into or out of a building.
Air barrier products may take several forms:
- Mechanically-attached membranes, also known as housewraps, usually a polyethylene-fiber or spun-bonded polyolefin, such as Tyvek is a generally accepted moisture barrier and an air barrier (ASTM E2178). (4)
- Self-adhered membranes, which are typically also a water-resistant barrier and a vapor barrier (4)
- Fluid-applied membranes, such as heavy-bodied paints or coatings including polymeric based and asphaltic based materials (4)
- Closed-cell medium density spray-applied polyurethane foam, which typically provides insulation as well (4)
- Some open-cell spray-applied polyurethane foam that are of high density (4)
- Boardstock, which includes 12 mm plywood or OSB, 25 mm extruded polystyrene, etc. (4)
Moisture Barrier Layer (1)
The Moisture Barrier Layer also called a vapor barrier (or vapour barrier) is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings to prevent interstitial condensation and of packaging. Technically, many of these materials are only vapor retarders as they have varying degrees of permeability. (4)Service Cavity (1)
Instead of having the services, other wise known as electric cabling and water lines, in side of the insulation later; the Passive House Building Standard has a separate layer dedicated to them that is also insulated (1). A service cavity makes a certain amount of sense as it keeps you from having to penetrate the insulation layer to run or repair your services. This allows you to maintain the integrity of the building envelope much better than having the services ran in the insulation layer while possibly increasing the ease to repair said services.Definitions
Water resistant and waterproof
Often refer to penetration of water in its liquid state and possibly under pressure (4) Under pressure, the water exploits butt joints, lap joints, nail holes, and other openings to flow inside (3). Even without wind, some water will migrate through tiny gaps to the back of siding through capillary action, the way water is siphoned up a stalk of celery.(3) This is true of brick, wood, and stucco, as well as the newest composite materials. (3)Damp proof
Refers to resistance to humidity or dampness. Permeation of water vapor through a material or structure is reported as a moisture vapor transmission rate (MVTR). (4)Resources
1. https://youtu.be/Hz6qomFM_dw2. https://www.phius.org/what-is-passive-building
3. https://inspectapedia.com/BestPractices/Water_Barriers_Exterior.php
4. https://en.wikipedia.org/wiki/
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