Bloomington Crawlspace Repair
Does Bloomington Crawlspace Repair encapsulation really work?
It’s funny because I never hear that question. There are more objections to closing the vents than any other subject. I think the question that is really being asked is; is it worth it? My answer would be; how much is it worth to eliminate the crawl space from having problems? How much does it cost to remediate Mold, or treat for termites? Is it really worth replacing your roof before it leaks? You can see where I’m going with this. You are probably here on this Bloomington Crawlspace Repair blog because you are having problems or you know someone that is. Aside from fixing anything that is currently wrong it really is an investment in keeping it from getting worse and costing you more. The average cost of repairing rotted joist is about $3500 now that is not for replacing all of them but it does pay for around 10 or 15 to be replaced. We did a job in Bloomington, IN in the fall of 2008 that needed 22 joist and 45′ of main beam replaced. It was a summer cabin the family used on the weekends and during Christmas time. The crawl space was 2200 sq. ft. and only 18″ high, a bit of a challenge I might add. The homeowner (Tom) knew it needed to be fixed and was having trouble finding a company that wasn’t trying to retire on his bank account. With this amount of damage it wasn’t hard to see why the salesman’s eyes would light up. In the end we installed a Bloomington Crawlspace Repair drain system and sump pump, closed seven foundation vents, our 16 Mil Bloomington Crawlspace vapor barrier and replaced the 22 rotted joists as well as the 45′ of main beam. The price? Well, the structure repair was $8500 and the rest was another $8000. Hardly chump change for a weekend home, but Tom really didn’t have any choice. It was that or rides it out until the floor fell in then walk away. I can tell you story after story about a homeowner that inherited, bought or neglected a problem crawl space. Either way it still hurts.
Lowering Crawl Space Humidity- Explained
Relative Humidity (RH) is the byproduct of two conditions in the atmosphere, temperature and dew point. To control or alter the RH you must manipulate either dew point or temperature.
Dew point temperature is the absolute measure of how much water vapor is in the air- Source The dew point is always less than the air temperature. The closer the dew point temperature is to the air temperature the closer the RH gets to 100%. Example- Dew point temperature 70F and air temperature 70F = 100% RH
If the home has an encapsulated with Bloomington Crawlspace Repair then the dew point inside the house will be different than that of outside the house. Air temperature will actually dictate what the RH is at any given dew point temperature. Inside the home we keep the air temperature at a comfortable level, say 70 degrees (which I am assuming is this case). A crawl space that has been sealed and encapsulated will maintain an air temperature similar to inside the living area. With that said, similar air temperature means about 5 degrees cooler than the living area. This is due to the consistent temperature of the earth under the vapor barrier, a geothermal effect. This is good in many ways for the home, because the air temperature will remain between 60F – 68F degrees most all of the time. Back to our RH problem, so the house (assuming) is 70F degrees (air temperature) puts our crawl space at (again assuming but will be close) 65F degrees (air temperature). In this scenario I will need to know either the dew point or RH to figure out the rest of the equation. In your email it states the RH levels so I will use them to find the dew point. Once I know the dew point I can show you what is going on in the crawl space and why it’s happening.
The assumptions-
House air temperature: 70F/49% RH
Crawl air temperature: 65F (house temperature minus 5 degrees)
Crawl RH: Unknown
Dew point temperature in the living area- 50F degrees
Using a dew point calculator to figure out RH in the crawl space with this information-
Crawl air temperature (assumption): 65F
Dew point temperature inside the home: 50F (also the dew point in the crawl)
Crawl Space RH is 60%
So you can see there is an 11% difference in RH levels between the home and the crawl space. The only difference is the air temperature between the two spaces. If you raise the air temperature in the crawl space to 70F, same as the living area, you will have the same RH 49%. Setting the dehumidifier at 49-51% means it is trying to lower the dew point temperature in order to achieve a lower RH. To successfully lower the dew point temperature in the crawl space you must lower it for the entire house. This is quite a task for any dehumidifier when you consider the traffic in and out of the house, the amount of showers taken, moisture from cooking, moisture in the wood inside the home and the natural moisture loss from each person living in the home. It will cause the dehumidifier to run more than 5 min an hour. If you wish to accomplish a shorter run time for the dehumidifier, then you can raise the air temperature in the crawl space. This can be done by conditioning the crawl space with air from the home, helping to deliver access heat to the coldest places- the crawl space. Of course when you raise the temperature to control RH, you make the RH level much more critical in the Mold growth equation (explained better in the next paragraph). The other option is to set the controls on the dehumidifier to a higher setting, maybe 58-60% (based on 65F degree air temperature). There are several factors in Mold growth; dew point temperature is only one of them (amount of moisture in the air), the other being air temperature. RH is simplified as a mixture of dew point temperature and air temperature. This simplification does not allow for any absolute rules, for example Mold will grow once RH reaches 55%. As a convenience to avoid teaching in depth classes on dew point temperature and air temperature each time a dehumidifier is sized and installed it is widely expressed- ‘to avoid mold growth, a safe RH is below 55%’. But, once RH is really understood that statement does not hold enough information. Last week, here in Indiana, our outside RH was 85% but the temperature was 31F degrees. Mold growth is not imminent in this equation because the air temperature is far too cold, but under the understanding of “less than 55%” it would be widely considered a mold growth threat. Just like RH is tweaked using air temperature, so is Mold growth. In a crawl space that has an air temperature below 70F will not generally be threatened by Mold growth until the RH rises past 67%. Keeping an encapsulated crawl space that has an air temperature of 67F and an RH of 58-60% will produce excellent results in the battle against wood rot, odor, Mold and mildew growth and a high electric bill caused by the dehumidifier. Of course the owner if the house has to add the crawl space to the list of maintenance duties required by the home, bi-annual crawl space inspections are strongly recommend by Bloomington Crawlspace Repair.