Ventilating a crawlspace for termite prevention
1. I had a termite contractor visit my home in Atlanta Georgia the other day. My house is 26 years old and has a crawlspace below the laundry room and the kitchen eating area. There is an unfinished basement under the rest of the house. The vendor told me I need to cut vents in the crawlspace in order to reduce the moisture which will cause floor warping and possibly lead to a haven for termites. I have read different recommendations on venting or not venting. What are the best recommendations for this crawlspace.
2. I am also having cold air leakage into the rooms above and unable to find the source of the leak from the crawl space. The floor is insulated with R41 worth of batt insulation and all pipe and electrical penetrations area foamed. There is an attic kneelwall area above both rooms. The floor is uninsulated and the soffit is blocked.
Any suggestions on these issues.
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Replies
#1 - while you have provided some information, there is a lot of factors that come into play - that said you want to solve the moisture issue & do so without inviting in more of that nice hot humid air into the crawlspace
#2 - ties in quite well with #1, and I recommend contacting Carl Seville, or if he is not interested / busy Allison Bailes of Energy Vanguard for another rater in the Atlanta area to not only help you find the real issues but how to solve them
Scott - in the hot and humid ATL cutting holes in your foundation will more than likely allow more moisture into your crawl space. First of all - why does he think you have a moisture issue? Did he take moisture readings of the floor joists or humidity readings in the crawl? If you do in fact have high moisture readings I would think you would be better off installing a continuous running exhaust fan. Good advice to consult with someone who understands building science and is familiar with your climate.
As for #2 - not really following you - need much more information - are you referring to rooms on the second floor of your home?
Scott - Your termite contractor is working from a script that his employer requires him to that has no basis in building science. If you can keep all the bulk moisture (water) out of your crawlspace through drainage and waterproofing, you can successfully keep it sealed. Install a solid moisture barrier on the floor made of reinforced polyethylene, sealed at all joints, at any piers, and at perimeter walls. You should air seal the rim joists with caulk or spray foam, and preferably insulate the walls of the crawl and basement, leaving a gap for inspections for termite tunnels. If you have a furnace and ducts in the area you should have enough space conditioning from various leaks in the system. If not, then you may need to add some ducts down there, or at least a dehumidifier to keep the space dry. Then find another termite contractor who understands that you can successfully seal a crawlspace and provide you with the service you need..
Danny,
My question #2 refers to my laundry room and kitchen eating area which are on the first floor located above the crawlspace. I have sealed and instulated the crawlspace floor but both these rooms are the coldest rooms in the house. I began to remove the flooring in the attic kneewall area to check for air infiltration from the soffits. I did not find any evidence of that. However, I did find that the area under this flooring was not insulated. Are there any other areas I am missing. The laundry room has a back stairwell behind it. It is located in the left rear of the house. The temperature difference between it and the kitchen eating area can be as high as 9 degrees. My only other thought is the cinder block foundation is leaking air up the walls. I have reinsulated all outside walls and the interior wall which the stair well shares with the room. The window in the room was replaced with triple pane one. I must be missing a major air leak here but I cannot locate it. Any suggestions would be helpful as we have a month and half of cold weather left.
If under the "flooring in the attic kneewall area" is also the ceiling of your laundry room - you most certainly need to air seal and insulate this area. Beyond that - hard to give much good advice without seing able to see it - sounds like a fairly tricky area. You want to create and air barrier and a thermal barrier around this entire room - check all accessible areas around the stairwell, block walls, etc - seal all holes and be sure all walls and ceiling around the room are insulated.
You mentioned knee wall upstairs in the attic - do you have finished space above within the knee walls? If so you need to continue your thermal and air barriers across the ceiling of the laundry (floor of the attic behind the kneewall) and up the knee wall. This often will result in the need to block between the ceiling joists/floor joists under the knee wall.
Scott - this detail may make more sense than my babble above:
https://www.greenbuildingadvisor.com/cad/detail/attic-knee-wall-insulated
I pretty much agree with what Carl recommended above with one minor exception. If your existing crawl has a musty smell or any signs of mold, mildew, etc. Than I do not think it is a good idea to put a supply in the there. I would prefer to use an exhaust fan as I mentioned above. The supply will put a positive pressure in you crawl pushing the moldy musty air up into your living space. The exhaust fan will remove the moisture laden and musty air and put a slight negative pressure on the crawlspace which will draw the makeup air from the conditioned area above. Both way are using the conditioned air in your crawl - the only difference is you are not mixig your crawl air with the rest of your house with the exhaust approach.