Indoor Air Quality

In an effort to reduce energy demands and increase comfort, modern construction techniques seek to isolate the interior of a home from the outdoor environment. This has resulted in increased insulation levels and reduced air leakage through the building shell. This tightening of the structure can potentially trap indoor pollution that has hence coined the term, Sick Building Syndrome or SBS.

EPA Indoor AirPLUS

Indoor pollution sources that release gases or particles into the air are the primary cause of air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not removing polluted air or by failing to introduce enough fresh air to dilute emissions from indoor sources.

Prior to the advent of air-conditioning, occupants opened windows and doors for ventilation. Even after AC became a standard option, most homes were poorly insulated and "leaky". As energy costs have risen in recent years, increased insulation and tighter construction techniques have changed the rules as they apply to the building shell and mechanical systems. Modern homes need a controlled mechanical ventilation system and in many cases should also include an independent source of dehumidification. Standard air-conditioning systems will likely not be adequate.

A healthy home provides immediate benefits to its occupants that may not be recognized or appreciated until after living with them for a little while. Fewer colds and allergies are the most common effect, but increased energy and sense of well-being have also been shown as beneficial side-effects of a healthy environment.

It's Not the Heat, It's the Humidity

My wife declares that she is burning up!

She is fanning herself with a magazine and obviously uncomfortable. However, the thermostat on the wall tells me that the temperature is the same as always for this time of the evening. The T-stat is programmable and the settings haven't been changed. How can she possibly be so hot?

To console her I drop the temperature two degrees, only to be shaking my head 20 minutes later when I see she has covered herself with a small blanket. My initial assumption is that her personal thermostat is broken.

There are some additional details that you need to know. It's early October here in Florida and the outdoor temperature is cooler than the peak of summer. Additionally, rain this afternoon cooled off the roof and inside the temperature is within our comfort range, without the use of air-conditioning. Here's what happened:

1. The AC system has not been running because of the pleasant temperature this time of year.
2. Humidity inside has slowly increased as a result of cooking, showers, laundry and even our breathing.
3. Increased humidity in the air prevents moisture on our skin from evaporating.
4. Comfort comes from a combination of temperature, humidity and air movement.

Camie was uncomfortable because the increased humidity prevented evaporation from her skin. When I turned on the AC, in addition to dropping the temperature two degrees it also removed the excess humidity in the room and created a draft. Admittedly, her personal T-stat is a bit more sensitive than mine, but she had just experienced a drastic change in all three of the components that affect comfort.

The Southern Home may need additional dehumidification during times of the year that pleasant temperatures prevent your AC system from operating. I wrote another article recently on the subject titled, All Southern Homes Need Dehumidification. Since running the AC is costly, a separate dehumidifier is worth considering to increase comfort during periods of Spring and Fall when temperatures are pleasant.

All Southern Homes Need Dehumidification

Ventilation and Dehumidification are critical talking points, especially here in Florida. Until recently they were discussed little, but the way we build homes is changing and they are now important issues.

A well-insulated home will maintain its temperature during moderate times of the year. As a result, the air-conditioning system will not operate very much. Typical thermostats only measure air temperature, but humidity, air movement and air quality all affect our comfort. Cooking, showers, and even breathing raise the humidity level in the home.
               
When the humidity level is too high, moisture ceases to evaporate from our skin making us feel clammy and sticky. Even light breezes lose their refreshing feel. High humidity levels support the growth of mold and mildew, and allow the air we breath to carry more impurities not present at lower levels.

Here in Florida during the spring and fall, without the use of air-conditioning, humidity levels will rise in the home causing uncomfortable and potentially even unhealthy conditions. Efficient dehumidification without the added expense of operating the AC or heating system, is the answer to lowering humidity levels and increasing comfort. We have several interesting articles available for view in our Building Science collection if you want to learn more.

To summarize: more insulation + tighter construction = less AC & more humidity. In an upcoming article I’ll discuss ventilation and its role in the southern home.

AC Ducts in the Attic

The Greenhouse Effect causes a typical attic to become super-heated in the summertime. For this and other very important reasons, we now realize that AC ductwork doesn’t belong in a typical vented attic. After 50 years of installing AC ducts in the wrong place, why are we just realizing this now?
First a little history lesson...

In 1947 mass-produced, low-cost window air conditioners became possible as a result of innovations by engineer Henry Galson, who set up production lines for a number of manufacturers. That year, 43,000 window air conditioners were sold in the United States. By 1969 more than half of new automobiles were equipped with air conditioning and most new homes were built with central AC.
(Ref. National Academy of Engineering. www.greatachievents.org)

In 1952, in Pompano Beach Florida, the metal plate connected engineered wood truss was invented and patented. The invention marked the beginning of the truss industry, that is still dominating building construction all over the world. (Ref. www.truss-frame.com )

It’s interesting to note that nearly all of the renowned Florida architectural styles pre-date World War II. After costs doubled during the 40’s and early 50’s because of increased cost of labor and materials, many new homes were downsized and simplified.  These modest homes proliferated across the American landscape. It was an extremely significant time in our country’s history with returning veterans from World War II and the Korean War, creating a huge need for simple, secure housing. Tract home communities sprang up across the country, and the suburbs were quickly filled with new homes - all part of the American dream.
(Ref. www.floridahistorichomes.com)

Additionally during this time period, mass-produced concrete blocks became readily available and spurred the growth of Florida concrete industry giants, Rinker and Florida Rock. At the time concrete block seemed like an ideal building material to fill the need for low-cost housing also fueled by population migration into the state. Hence, the now well-known basic Florida construction style developed: slab-on-grade; concrete block walls; and engineered wood trusses for the roof structure.

Since most homes in Florida were built without basements, the attic became a convenient place to install the AC ducts. Energy was cheap and air-conditioning was a welcome necessity, so until recently AC ducts have been going into a typical attic and few builders and designers ever considered otherwise.

There was a brief interest in increased energy efficiency after the OPEC oil embargo of the 1970’s, but it quickly faded as the affluence and growth of the American economy influenced the purchasing decisions of home buyers and builders. In another post, I’ll discuss how this same affluence has degraded building performance and brainwashed the consumer into comparing homes using cost-per-square-foot analysis.

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