Do I need a vapor barrier when using your home insulation?Updated 2 months ago

Vapor Barrier? No.

Vapor Open Air Barrier? Yes!

Short Answer: We recommend a vapor open-air barrier with Havelock Wool. You should not use a traditional vapor barrier. (Always check local building code too.) 

Some details : 

A vapor barrier limits the movement of water vapor through walls. Different materials allow varying amounts of moisture to pass. For example, about a third of a quart of water can diffuse through an 8’ x 4’ section of drywall in a heating season, vapor barriers help prevent this.

An air barrier blocks air flow into the wall assembly, which carries much more moisture than diffusion alone. Using the same drywall example, roughly 30 quarts of water can move through via air leakage. That’s why building science emphasizes controlling air movement over vapor diffusion to prevent moisture problems.

What is a Vapor Open Air Barrier?

Moisture will inevitably enter walls, and trapping it can lead to mold and mildew. Traditional vapor barriers prevent moisture from passing through, but if moisture gets trapped, it can cause damage. Modern building science favors a vapor-open approach, which allows walls to dry inward, outward, or both.

A vapor-open air barrier combines airtightness with moisture management: it stays tight in winter to keep moisture out, but becomes more permeable in summer to let trapped moisture escape, helping walls stay dry and healthy.

 Here is one we recommend.

Where do I put this Air Barrier?

Air barriers can go outside the insulation to block air at the source (like wind) or inside the insulation. Ideally, both locations can help, but the most effective approach is to control air on the exterior, then let wool insulation inside the walls manage moisture naturally..