CLOSED CRAWLSPACES What s In the Crawlspace? Wet Sagging Fiberglass Improper Drainage Have you ever been in your crawlspace? If not, have you ever even opened the door to look inside and see what it looked like? For many homeowners, crawlspaces epitomize the old saying, Out of sight, out of mind! The scary thing is that many of the problems that are occurring in your crawlspace might as well be occurring in your living space. The crawlspace and the living area of your home are both connected and they directly interact. Studies estimate that as much as 50 percent of the air in your home has been in the crawlspace at one time. Air is a carrier and it brings moisture, mold, mildew, dust, pesticides, insulation, radon, and other unwanted contaminants with it. See www.crawlspaces.org. For years, building codes and conventional wisdom have prescribed ventilation with outside air as the primary method of moisture control in crawlspaces. Most everyone naively believed that somehow the good air would flow into the foundation vents and that the bad air would somehow be flushed out of the same vents while taking the moisture with it. In the humid South, ventilation with outside air only makes moisture problems worse. There is now overwhelming evidence that proves that traditional methods of constructing All rights reserved by Synergy Airflow and Ventilation, LLC Page 1
crawlspaces with foundation vents is completely wrong. Synergy Airflow and Ventilation offers a new type of crawlspace construction that eliminates vents to the outside as well as traditional fiberglass batt insulation under the flooring. Our new closed crawlspace construction techniques will greatly improve moisture control while significantly reducing energy costs. A Closed Crawlspace Foaming the Crawlspace Closed Crawlspace Termite Viewing Strip Foundation vents need to be either eliminated or closed in the South, if only in the humid spring and summertime. To understand why, you need to understand relative humidity and dew points. For years, I listened to my local weather person announce the relative humidity and dew point for the day but I never knew what he or she was talking about. It is a relatively simple concept. The amount of moisture that air can hold is determined by its temperature. Warm air can hold more moisture than cold air and vice versa. Relative humidity is the ratio of the amount of moisture contained in the air compared to the maximum amount of moisture the same air can hold at a given temperature. For example, air holding half the maximum amount of moisture it is capable of holding at a given temperature has a relative humidity of 50 percent. Air holding the maximum amount of moisture possible at a specific temperature has a relative humidity of 100 percent. At 100 percent relative humidity, the air is said to be saturated. It has reached its dew point and the vapor turns into water. Take a All rights reserved by Synergy Airflow and Ventilation, LLC Page 2
sample of air at 95 degrees and 90 percent relative humidity. This is pretty standard Alabama summertime air. It only takes a drop in temperature of a few degrees to cause the relative humidity to go up to 100 percent which is the saturation point or dew point. This is the main problem we are fighting with air-transported moisture in our area. We are attempting to dry out our crawlspaces by bringing in hot, humid outside air that condenses on cool crawlspace surfaces in the summertime. It amazes me that there are companies that continue to sell motorized foundation vents that actively bring in hot, humid outside air in an attempt to dry out foundations. When I tell them that what they are doing is wrong and that it is actually causing the problem, they look at me like I am the stupidest person in the world. But have you noticed all of the foundation repair companies that are now advertising on television, newspaper, and the radio? There are unbelievable problems going on in new and existing crawlspaces that must be addressed. A Thermostatically Controlled Foundation Vent A Supply Vent Next to Foundation Vents Serious Condensation Improperly insulated and leaking HVAC supply ducts dump cool air into the crawlspace. The temperature of the framing members, ducts, plumbing, etc. are below the dew point of the outside ventilation air which allows condensation and creates fertile areas for mold growth. In a best case scenario, we recommend All rights reserved by Synergy Airflow and Ventilation, LLC Page 3
that HVAC ducts should be brought into the conditioned space to avoid most moisture and/or condensation problems. Bringing ducts into the conditioned space eliminates the thermal penalty as well. Otherwise, HVAC ducts that are installed in the crawlspace or attic must be completely sealed and insulated to minimize duct leakage. We offer HVAC equipment load calculations (Manual J) and HVAC duct design and sizing (Manual D) as well as other consulting services to help you avoid these problems. We have testing services where we use a Duct-blaster which is a piece of equipment that blows air into your ducts and measures the amount of duct leakage. We have a fog machine that we use in conjunction with the duct-blaster to physically see where the ducts are leaking. Plumbing has to be pressure tested to insure that it does not leak. Why is ductwork any different? As a simple test, open the access hole to your crawlspace during the summertime and if you can feel cold air leak out, your ducts are leaking. Manual J Blower Door Duct Blaster Mold requires five (5) things in order to flourish: mold spores, oxygen, food, temperatures between 40F and 100F, and relative humidity over 70 percent (moisture). The first four are difficult to control. Mold and All rights reserved by Synergy Airflow and Ventilation, LLC Page 4
oxygen are always present. It is impossible to eliminate them. Almost every product within a home is great mold food especially sheetrock. Most people refuse to live in a house with temperatures below 40 degrees or above 100 degrees. Relative humidity is by far the easiest to control. Ideal health and comfort for humans occurs at 30 percent to 50 percent relative humidity. This can be a daunting task when we consider that we routinely experience outside humidity levels of 90 percent or better, and most wall vented crawlspaces are found to have humidity levels that are very close to the outside air. Microban Mold on Joist in Crawlspace There is a serious problem with having one prescriptive building code for all of the different conditions in the U.S. Ventilating crawlspaces with dry air is a good idea in some parts of the country, but when do we ever have dry air here in Alabama? The 2003 IRC code, Section R408 calls for foundation vents but allows for elimination if any one of five exceptions is met. It is The humidity was 89 percent in this crawlspace. All rights reserved by Synergy Airflow and Ventilation, LLC Page 5
mandatory that you meet one or more of these exceptions and that you have pre-approval from the inspection department. 1. Where warranted by climatic conditions, ventilation openings to the outdoors are not required if ventilation openings to the interior are provided. 2. The total area of ventilation openings may be reduced to 1/1500 of the under-floor area where the ground surface is treated with an approved vapor retarder material and the required openings are placed so as to provide cross-ventilation of the space. The installation of operable louvers shall not be prohibited. 3. Under-floor spaces used as supply plenums for distribution of heated and cooled air shall comply with the requirements of Section M1601.4. 4. Ventilation openings are not required where continuously operated mechanical ventilation is provided at a rate of 1.0 cfm for each 50 square feet of under-floor space floor area and ground surface is covered with an approved vapor retarder material. 5. Ventilation openings are not required when the ground surface is covered with an approved vapor retarder material, the space is supplied with conditioned air and the perimeter walls are insulated in accordance with Section N1102.1.7. The IRC 2004 Supplement, the 2006 IRC, and the 2009 IRC has eliminated these five requirements. It allows closed crawlspace construction if (1) there is a sealed ground vapor retarder, (2) the perimeter walls are insulated in accordance with Section N1102.2.8, and (3) if the crawlspace is designed with either an All rights reserved by Synergy Airflow and Ventilation, LLC Page 6
exhaust ventilation system with an air pathway to the common area or a conditioned air supply with a return air pathway to the common area. It is very important to know what IRC edition your building department uses. We have also learned in the last few years that if insulation is not touching the air barrier it is not working. That is the case with all types of insulation except for foam insulation which also serves as an air barrier. For example, your skin is your air barrier and a blanket is the insulation. If you hold the blanket several inches from your body, it does not work. The same is true for most insulation. In the case of fiberglass batts installed in floor joists, it is virtually impossible to install the batt where it is in complete contact with the sub-flooring. Fiberglass batts are fighting gravity and will almost always pull away from the sub-flooring. Many of the joist cavities are not built exactly on center and in wide cavities the batt oftentimes completely falls out. In narrow cavities, the batt is compressed and the amount of compression is equal to the amount of R-value loss. Plumbing, wiring, ducting, etc. makes it virtually impossible to install the batts in contact with the sub-flooring. Plumbers, electricians, HVAC technicians, and cable installers oftentimes pull it out and do not replace it. Many times the batt is pulled down when it is wetted with moisture from the air. I have installed batts in the crawlspace of my own home. I have installed batts in hundreds of homes under construction and in hundreds of existing homes. I have supervised crews installing batts, and I have sold batts in hundreds if not thousands of crawlspaces. Traditional crawlspace insulation in floor joists does not work and it is a waste of money. For years, I have advised anyone that would listen not to insulate the All rights reserved by Synergy Airflow and Ventilation, LLC Page 7
floor joist. But in many jurisdictions, the code required it. With closed crawlspaces, the IRC allows the elimination of insulation in the floor system if the walls of the crawlspace are insulated properly. However, there are strict requirements regarding protection from termites and fire. Proper planning, design, and installation by Synergy Airflow and Ventilation is recommended. However, it is mandatory that you get prior approval from your local building officials. VS. Batt Insulation Not Touching Flooring Foam in Contact with Flooring Notice the Foundation Vents Have Been Foamed Over All rights reserved by Synergy Airflow and Ventilation, LLC Page 8
General Steps to Constructing a Closed Crawlspace: It is recommended to have the interior grade of the crawlspace built up several inches above the exterior grade and then drain it at its lowest point. You never want the interior grade of the crawlspace lower than the exterior grade. Otherwise, water pools into the Moisture Problem in Plain View crawlspace. It is mandatory to provide proper drainage both around and inside the crawlspace and that you dry out the crawlspace before sealing it up. A portable dehumidifier used in conjunction with a fan is a great way to dry out the crawlspace. Dehumidifier All rights reserved by Synergy Airflow and Ventilation, LLC Page 9
Make sure that the ground outside of the crawlspace is sloped away from the home at a rate of 6 inches of fall for every 10 feet of run. foundation. Make sure gutters are properly installed and drained away from the No Gutters Sidewalk Holding Water Incorrectly Drained Gutters Efflorescence Correctly Drained Gutters Make sure the exterior of foundation walls are damp-proofed. Waterproof Walls All rights reserved by Synergy Airflow and Ventilation, LLC Page 10
Six-mil Black Poly should go down immediately on the ground in the crawlspace as soon as the house is blacked in. Moisture from rain should be prevented from pooling on it during construction. 6-mil black poly ground cover needs to be continuous, overlapped, and sealed correctly in the crawlspace. Piers in crawlspaces need to be wrapped in poly or have it under them in order to stop moisture from the ground moving up through them and evaporating into the crawlspace. Poly needs to be sealed to the interior walls of the foundation for the same reasons. Seemingly dry foundations can allow 12 to 13 gallons of water to evaporate daily into Wrapped Piers the building from the soil. A minimum 1 viewing strip needs to be left between the bottom of the framing and the top of the concrete block in order to inspect for termites. There are many different ways to insulate the crawlspace walls. Dow Blueboard or spray applied closed cell foam is my preferred way because it serves as the air barrier and the thermal barrier. Thermal barrier and termite protection code requirements must be followed. Closed Cell Foam All rights reserved by Synergy Airflow and Ventilation, LLC Page 11
A sealed crawlspace is usually close to the temperature inside the home. It is a great place to install ducts without the energy penalty from heat gain or heat loss that is associated with an unconditioned crawlspace or attic. Monitor Your Foundation Make sure the crawlspace hatch cover is foamed and air sealed. Make sure the condensate from the HVAC system is planned for and drained away from the crawlspace. Sprinkler systems need to be kept away from the foundation. Do not locate the air handler and condensate drains in the crawlspace. No Plastic Under Air Handler Do not terminate dryer exhaust into the crawlspace for any reason. Do not terminate bathroom exhaust fans or kitchen exhaust fans into the crawlspace for any reason. Controlling moisture almost eliminates rodents and other insects such as spiders and termites. All rights reserved by Synergy Airflow and Ventilation, LLC Page 12
The elimination of standard fiberglass batt insulation installed in the floor joist eliminates its ability to serve as a medium to collect dusts, moisture, insects, rodents, etc. Controlling crawlspace moisture prevents buckling of hardwood floors. Wood does not need to be dried to below 12 percent moisture content. Closed crawlspaces reduce moisture levels during the summer and slightly elevate moisture levels in the wintertime. This produces a more constant humidity level that reduces shrinkage and expansion of construction materials. Controlling crawlspace moisture prevents loading the carpet and the carpet padding with moisture that provides a growth medium for dust mites, mold and mildew. I recommend taking it a step further and completely eliminating carpet in your home. Do not build a sealed crawlspace without thorough planning and consultation. Some homes cannot be built with a sealed crawlspace because of high ground water levels or improper drainage. It is recommended to have a remote controlled hygrothermometer installed in your crawlspace to monitor the humidity and temperature. There are three (3) choices of drying the crawlspace. Install a dehumidifier, supply ducts, or exhaust fans. All rights reserved by Synergy Airflow and Ventilation, LLC Page 13
Make sure radon vents are installed properly. Improperly Installed Radon Vent The cost of a sealed crawlspace is about the same as a traditional crawlspace with floor insulation or maybe even slightly less. Make sure your crawlspace is routinely inspected for moisture issues. Flooding or leaks must be taken care of immediately. Monitor Your Foundation Any workers in your closed crawlspace must be informed that damage to the vapor barrier will not be tolerated. Make sure that there are no combustion engines such as lawnmowers stored in your crawlspace. Make sure there are no toxic products stored in your crawlspace. The crawlspace should be separated from adjoining basements, porches, and garages by permanent walls and air sealed. All penetrations to the exterior must be air sealed. All rights reserved by Synergy Airflow and Ventilation, LLC Page 14
All construction debris must be removed from the crawlspace. Moisture and Garbage I built my own crawlspace this way when I built my own home and I am a true believer in it! Be sure to consult www.crawlspaces.org. Call or email us for an estimate to close your crawlspace in your new or existing home. All rights reserved by Synergy Airflow and Ventilation, LLC Page 15