Florida Crawlspace Homes

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Few of our Florida homes have basements but a great many have elevated finish floors over what is commonly termed a “crawlspace.” A crawlspace is the open area/gap between the finished floor and the ground. They vary in height and accessibility. Some have as little as a few inches between the floor joists and ground while some can be several feet. The height or open space depends upon the terrain or height needed (at the time of construction) to protect the home from flooding.

Most of our homes with crawlspaces were built prior to the 1970’s. Our classic home designs of the period between the 1880’s through the early 1940’s included an elevated front porch and large windows for ventilation. Air conditioning was not routinely installed in our homes until the 1970’s! Our homes were designed to “breathe” so they could dry out when they got wet. Popular designs included Cape Cod, American Craftsman, Colonial Revival, Georgian, Federal Colonial and Victorian.

These styles changed to Usonian (Frank Lloyd Wright), Minimal Traditional, Mid-Century Modern, and the ever-popular Ranch after World War II (late 1940’s). The housing boom of the 1950’s required homes to be built faster and the production “tract” home was invented (Levittown). The crawlspace gave way to slab-on-grade construction. If the building lot was in a flood-prone area, we raised the lot grade by adding soil to bring the home elevation up. If we wanted an elevated front porch, we built the home on a stem-wall. A stem-wall is an elevated footer (typically 3-4 concrete blocks high) with the interior of the footer filled with compacted soils); you have a slab-on-grade with the grade being 2-3 feet high.

There were few issues with our crawlspace homes during the period. The crawlspaces were mostly open and well ventilated. We did not have air conditioning, so we kept our doors and windows open while using screens to keep insects outside. When our homes got wet, the warm Florida breezes dried the wood. We used old, hard wood which helped to protect us from wood rot and termites.

Our issues with damp crawlspaces, mold, mildew and termites began when we introduced air conditioning to these homes. When the wood did get wet, it could no longer dry as we removed all-natural ventilation. We blocked the crawlspace with walls and landscaping which reduced ventilation. Our floors were always cool from the air conditioning. We added AC ducts in the crawlspace which helped to cool the space (duct leakage and condensation) and further reduced the ability for the materials to dry. (Note: cold air does not dry wet wood).

Often, we added ducts which simply do not fit in the space, so our ducts are in contact with soil and water when we do get elevated water conditions. The ducts are not water-tight so we now have standing water or wet insulation inside the ducts. This creates a condition which is conducive to bacteria growth.

The simple fact is these homes were not designed for the modern comfort we expect today. Most of these homes were poorly insulated (if at all). You see if you want a home to naturally ventilate and dry, you don’t install insulation!

The air from damp/wet crawlspaces is mechanically drawn into the home when we run our air conditioner system. The air intake (supply side) of the air handler pulls air into the system and that creates a “venturi” effect. Air will be drawn in around any gap/crack in our floors, walls, windows, ceilings and doors. In the most basic principle of energy movement, heat chases cold, so the warmer air in the crawlspace wants to “chase” the cooler air inside the home. The air handler was not designed to treat all this “outside” air, so we have elevated humidity inside the home. The air handler simply cannot strip all this water vapor from the air.

So, we now have a compounded effect on our indoor air quality. We have wet/damp conditions in the crawlspace, we may have wet/damp insulation in our ducts and we have elevated humidity inside the home. Generally, we will see white wood rot on the wood joists or flooring and if the moisture is consistent and high enough, we may find curvularia mold and/or erisiphye (mildew).

All these conditions are treatable and preventable.

Wood destroying fungi and mold can be treated. The mold/mildew can be removed with products such as Shockwave and the wood destroying fungi can be treated with BoraCare or Timbor.

Re-working or replacing the ducts can be more challenging. They need to be secured above any high water line. If sufficient room is not available, we will need to modify the equipment and duct placement which may require different equipment or remodeling the home to accommodate the equipment/ducts. Unfortunately, there is no shortcut to this process.

Many will advise you to encapsulate the crawlspace but that is not the best option.

While this may be a good option in drier climates, it almost never is in Florida. Unless you can stop the water infiltration into the crawlspace (mostly impossible), in time the water will float or damage the visqueen barrier rendering the encapsulation obsolete. Further, you will be required to install mechanical dehumidification as you have created a whole new ecosystem in this “terrarium.” You still have hot, moist, humid air in the crawlspace which will create condensation so unless you are mechanically dehumidifying the area, you will still have a moisture issue. If you install a visqueen vapor barrier beneath the floor joists this condensation will form and deposit moisture between the plastic barrier and your wood joists/flooring. You have really not accomplished anything and now you have a extra mechanical systems (dehumidifier and sump pump) to maintain and eventually replace. It is a short term solution.

Is there anything that does work?

Yes, but it will always require modification and money. However, the money you spend will be a long-term solution. You can’t change or alter rising water in most cases, so you must be able to control it when it does occur. Improving site and crawlspace grading is first and foremost. Most people have never investigated their crawlspace let alone clean it up. We find trash piles, debris piles, rotted wood, old furniture and more in crawlspaces. Plumbers and AC contractors are notorious for digging holes to make their work easier and these holes fill up with water. Over 80% of the crawlspaces we inspect do not have any floor insulation. The crawlspace should drain away from the home. You may need some drainage piping and even a sump pump.

The second biggest issue we find is improper ventilation. Building code requires a minimum of 1 square feet for each 150 square feet of under-floor space. Further at least one vent should be within three feet of each building corner. There are different ways you can achieve this but meeting the minimum code requirement is generally not enough ventilation for our Florida homes. Personally, I believe you need to triple this sizing recommendation. The more air flow, the better. Building codes also does not take into account if we have restricted air flow due to being in a dense, urban setting. The code assumes your home receives air flow from all directions and that is just not typical in a city type setting.

Another issue we find is people blocking the ventilation with dense shrubbery which further restricts air flow. Keep the vents open and clear of any vegetation.

Insulate the floor and seal all gaps/cracks/penetrations into the floors especially around ducts and plumbing connections. Remember, each time your air handler turns on it is creating a draw from your crawlspace and it is pulling that dusty, damp air from the crawl into your air stream.

Re-work AC ducts to get them off the ground and above any high-water mark. If that is not feasible, you need to consider modifying the HVAC system to get the ducts out of the crawlspace. This may be expensive and you may need to plan this in stages.

Have your home inspected by an indoor air quality expert.

If you call a “crawlspace company,” all you will hear is “encapsulate” but that is rarely the best long-term solution. It also is not cheap and encapsulation with mechanical controls may cost as much, or more, than re-working your AC system to get it out of the crawl.

If you are in the Jacksonville or Orlando areas, give us a call to schedule an inspection. We don’t sell encapsulation or anything other than quality air consulting.

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