help with mold

Closed Thread

Old 08-19-04, 11:42 AM
Visiting Guest
Posts: n/a
Question help with mold

I have a house in Pacific grove california with a mold problem in an addition. I don't see visible mildew, but get a musty smell if I leave an area rug, etc. on the floor. I want to carpet the room, but need to correct the problem first. The crawl space has vents, but still has too high of a moisture level. I put down plastic over the ground and grading is fine. The problem is Pacific grove is foggier than San Francisco. Almost every day (year round) is about 65 degrees with a low of about 55. We have sun less often than clouds or fog and often have mist in the morning and evening. There is no insulation in the house except foam boards on top of the vaulted ceiling (between ceiling and roofing material).
I can install a fan in the crawl space but not sure if that will help much as the outside air is often at or near saturation. I am not sure if insulating the top of crawl space (below floor) will help or not. What about a vapor barrier?
The construction of the addition is 2 1/2 inch thick tongue and groove "deck boards" over the floor joists then a tar paper layer with 1/8 inch plywood over that to make the floor level with existing house. My plan is to rip out the plywood and tar paper. Treat the deck boards with fungicide from above and from the crawlspace (also treat joists from crawlspace), but then where should I put vapor barriers and/or insulation?
I was thinking maybe putting poly down over the deck boards before putting down new plywood. Then maybe insulation (with paper facing up toward floor), but then I am still worried about moisture in the air below. Could I do something like Tyvek below the insulation? I know that sounds odd, but remember my moisture problem isn't like hot humid weather elsewhere in the country. I have condensation on almost every surface each morning. I was thinking I need something more permeable to moisture than the poly above so moisture doesn't get trapped between, but something that would slow down the influx of moisture from the foggy air. Should I skip the tyvek but install my insulation with the paper out (toward the crawl space)? Or should I skip the insulation but install poly above and tyvek below?
Sponsored Links
Old 08-19-04, 03:39 PM
Join Date: Aug 2004
Location: USA
Posts: 215
I used to live in Monterey (Skyline Drive area) and know what you mean. You definitely need to insulate and install vapor barriers, if only to reduce condensation on interior surfaces and within the walls and subfloors. You also need to look at your gutters and downspouts -- I know, you only get 10" of rain a year, but frequent drizzle, poor drainage, and low evaporation rates can cause quite a bit of water to collect around the foundation and in your crawl space. If you have Monterey pines too close to the house (branches hanging over the roof) you should have an arborist trim them back or remove them (if the city will allow). Mildew loves to grow in the shade of these pines.

I would get an insulation specialist familiar with your climate to look at your problem.
Old 08-19-04, 04:36 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389

I think that you should do the crawl space like we do to all.
Seal up the vents 6 mil poly on the ground 2' over lap and tape the seams.Up the walls some there. A 2" polystrene on the walls up to the joist. Put R 19 in the joist space cut to fit tight right up there on the sill plate all around the home. Id put a Dehumidifier down there in the crawl just for back up . go look at and read it

Old 09-01-04, 10:16 PM
Join Date: Nov 2001
Location: USA
Posts: 1,873

There are a couple of topics on this site that will help you decide on the best approach for you to control the moisture problem. Two I strongly recommend are "Thermal/Moisture Dynamic" and the last topic on this page "Air/Vapor Barriers".

Ventilation for areas of the home is somewhat confusing to most people. For example, attic ventilation is recommended regardless of the type of climate you live in. The reason for this is because of the low moisture permability of roofing materials that would trap moisture inside the attic space if there was no ventilation. In other words, attic ventilation allows moisture to bypass the roofing materials.

Whereas with crawl space ventilation, it depends on the amount of humidity in the outside air. For example, in colder climates the air outside usually possesses less humidity than the crawl space, ventilation is appropriate. In hot humid climates, the air outside usually contains more humidity than in the crawl space, ventilation is inappropriate.

I know what you are thinking and that is if this applies to a crawl space, why not for an attic space? There are several reasons beside the low moisture vapor permability of roofing materials. They are warm air condenses on cooler surfaces and they bouyancy of warm air; and Relative Humidity (RH%).

Understanding the Thermal/Moisture Dynamic and to get rid of the condensation on surfaces you experience in the morning is best when you experience a simple solution yourself. A simple test is to raise the temperature slightly in the early morning hours in the affected area. Either by using your heating system or space heater. I do not expect you to take my word on this, seeing is believing.
Old 09-02-04, 07:38 AM
Banned. Rule And/Or Policy Violation
Join Date: Jul 2004
Location: Champane, Il
Posts: 12
Crawl Space insul


You do need to seal the vents and all holes and cracks. xxxxx at xxxxxxxxxxx developed the following method about 20 yrs ago and I haven't found anything that works as well as his method.

Attach a 4 mil VB to the side of the sill plate. Let hang down and across the floor. Cover remaining area over lapping about 6". Install second layer cross wise, but not up the wall. To keep the temp within 2 - 3 degs of up stairs and to prevent condensation, install a radiant barrier material (RB) 51" wide to the sill plate, over VB and let hang to ground. DO NOT use FG. IT WILL CONDENSATE. It not only causes mold but raises the moisture level to where the wood will rot.

Cut RB panels to install between joists at rim board.

The comments about down spouts and trees is good advice. Bushes and other close vegetation can cause problems.

If you do not have insulation in walls you have a mixed condition. FG causes condensation, so the lack of it helps reduce the amount of moisture pumped into the house. How ever you still have humidity penetration. xxxxxxx

If you want to improve the insulation values of the ceiling you can do so with the RB. xxxxxxx

Last edited by twelvepole; 09-18-04 at 02:45 PM. Reason: Posting email address and commercial website
Old 09-02-04, 10:14 PM
Join Date: Nov 2001
Location: USA
Posts: 1,873

This site lists the most prominant Energy conservation websites within and outside the United States. It is put together by the US Department of Energy, Energy Information Administration. My website is listed on this webpage and you can easily find it because it is the only Independent website listed. I am an Independent because I refuse to be associated with the government, any organization, company or product. Primarily because I do not wish my views to be tainted by any such association.

Several years ago, I allowed myself to be associated with an notable organization on a particular subject, Sustainable Healthy Indoor Environments. This stemmed from the controversy over Sick Building Syndrome (SBS). Unfortunately this organization's agenda went far beyond this particular issue and my opponents to the issue used it to discredit my view.

As a Moderator for this forum, my responsibility is to encourage the expression of others who use this forum. I am a Moderator primarily because of my experience, knowledge and reputation in this particular field.

Last edited by resercon; 09-05-04 at 08:25 PM.
Closed Thread

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes