08:38AM | 12/13/02
Member Since: 12/12/02
1 lifetime posts
I am interested in opinions, experiences etc. regarding the necessity of placing house wrap under vinyl siding. I am in south carolina at the coast. The IRC 2000 code and our building dept. say that house wrap in not required under vinyl siding however, alot of people are using it under vinyl siding and there is a debate seeming to begin to take place as to is house wrap a contributing factor in the mold issues arising now. I've read articles that insinuate that house wrap and tighter houses may have something to do with the increases of mold. My basic questions are: 1. what may happen if I do not use house wrap 2. If vinyl siding breaths will water behind it produce a problem 3. If I use house wrap and water gets behind it what may happen. Please express opinions good or bad. My vinyl installer says It seems that about 50% use wrap as standard under vinyl about 50% recommend not using house wrap as the vinyl siding breaths. Is this an unecessary expense or am I being penny wise and pound foolish to say I do not want to pay for it if it has no absolute benefit. I do have a plastic vapor barrier between my insulation and my drywall. THANK YOU FOR TAKING THE TIME TO RESPOND !!!!!!


01:34PM | 12/13/02
Member Since: 06/03/01
327 lifetime posts
This is going to be a very personal decision. House wrap does breathe but is waterproof. It does allow water vapor to pass thru. It's main purpose is to seal the many air leaks in the typical house. This is a great help to complete the overall insulation of a home and will help your heating & cooling bills. On the other hand, it does help seal the home which can contribute to increased mould if proper ventilation is not installed. This is where a good air-to-air heat recovery ventilator comes in. It exhausts the inside stale & moist air while bringing in fresh outside air and saves most of the heat (or cool) from the exhausted inside air.

[This message has been edited by LDoyle (edited December 13, 2002).]


04:39AM | 02/08/03
Member Since: 02/07/03
13 lifetime posts
There is a website Journal of Light Construction which has an article on "The Proper way to install house wrap". House wrap was made for vinyl house. 15# paper is for brick exteriors.
Water gets behind brick, vinyl and stucco. It does, that is fact.
The idea is that you are protecting the sheathing from water, not water vapor. The wrap cuts wind but does not stop air. It is like Gore Tex is the clothing industry.

There is no wrapping school. It is a product that has put out there for contractors to use. No one has told them how to use it properly. Now whether it is used correctly is another is OUR problem. I see it misapplied constantly around here.
If you apply it so water get behind it, then you are going to have moisture problems. There are many ways to misapply this product, like any product.
Home building codes have attempted to improve energy efficiency without looking at the effects these changes make. Moisture problems are one of these problems.
Try building science .com for usefull info on home construction practices


04:50PM | 02/08/03
Member Since: 01/28/03
693 lifetime posts
Housewrap has no bearing on mold growth.

Mold requires moisture and darkness to grow.

Housewrap does not contribute in any way to increasing moisture or darkness in a home.

As already mentioned, housewrap is an air barrier but it allows the free flow of water vapor to pass thru.

Behind all sidings you need a secondary weather barrier. The purpose of a secondary weather barrier is to prevent wind and sun borne moisture from pentetrating the siding and damaging the sheathing.

Housewrap is but one such secondary weather barrier and in fact #15 or 30 lb roof felt performs better in most circumstances. Foam boards can also be used as secondary weather barriers.

Here is a helpful link:



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