It is not uncommon for HVAC equipment to be located in an attic. Generally, that attic is not a conditioned space, so humidity levels may be high. If high humidity is present, there is a great danger of having condensation from the A/C equipment. This can lead to insulation damage, collapse of ceiling drywall below, and mold.
To avoid these problems, it is important to maintain a vapor seal between the cold surfaces and the attic air. Do this by installing a vapor barrier on the outside of the duct and equipment insulation.
Monday, March 22, 2010
Tuesday, March 16, 2010
Blue Water in the Desert
Why would someone's domestic water turn blue, be toxic and slippery?
I was called in to find out what was causing these problems, which made the homeowners use only bottled water in their brand new home.
After considerable investigation, including talking to several chemistry professors, I found that the cause of the problem was a combination of high pH water and bronze pipe fittings. A phenomenon called "zincification" causes the zinc in the metal compound to go into solution in the presence of his pH water. Some of the copper also goes into solution, and combines with OH molecules, forming copper hydroxide, witch is toxic, slippery, and blue. QED
Watch out for PEX pipe with brass or bronze fittings if the water has a high pH.
I was called in to find out what was causing these problems, which made the homeowners use only bottled water in their brand new home.
After considerable investigation, including talking to several chemistry professors, I found that the cause of the problem was a combination of high pH water and bronze pipe fittings. A phenomenon called "zincification" causes the zinc in the metal compound to go into solution in the presence of his pH water. Some of the copper also goes into solution, and combines with OH molecules, forming copper hydroxide, witch is toxic, slippery, and blue. QED
Watch out for PEX pipe with brass or bronze fittings if the water has a high pH.
Thursday, March 11, 2010
FLORIDA MOLD
WHERE DID THAT MOLD COME FROM?
In a 6 month old building, metal surfaces were rusting, and mold was everywhere. Vinyl wall coverings were coming unglued. What was the cause?
The air conditioning system in this building employed small (5 tons or less)direct expansion units. The fans units ran continuously,and included fixed outside air intakes. All of the equipment was sized for a peak daytime cooling load with high outdoor temperatures and sun. In many cases two small cooling units served a single space.
We took temperature and humidity measurements, and found that the indoor humidity level was well above 60%. I theorized that during moderate weather, the compressors would cycle on temperature, but the high humidity outdoor air would continue to be introduced to the space, as the fans ran all the time. When a compressor would come on, the cold air from the system would cause condensate of the highly humid air.
Our solution was to disable half of the cooling units. This allowed for longer operation of the remaining equipment, allowing for better dehumidification. After about an hour in this operational mode, the indoor humidity dropped from 63% to 51%, solving the problem.
After confirming the solution, we made some duct and temperature controls modifications, and the humidity and mold problem was solved.
In a 6 month old building, metal surfaces were rusting, and mold was everywhere. Vinyl wall coverings were coming unglued. What was the cause?
The air conditioning system in this building employed small (5 tons or less)direct expansion units. The fans units ran continuously,and included fixed outside air intakes. All of the equipment was sized for a peak daytime cooling load with high outdoor temperatures and sun. In many cases two small cooling units served a single space.
We took temperature and humidity measurements, and found that the indoor humidity level was well above 60%. I theorized that during moderate weather, the compressors would cycle on temperature, but the high humidity outdoor air would continue to be introduced to the space, as the fans ran all the time. When a compressor would come on, the cold air from the system would cause condensate of the highly humid air.
Our solution was to disable half of the cooling units. This allowed for longer operation of the remaining equipment, allowing for better dehumidification. After about an hour in this operational mode, the indoor humidity dropped from 63% to 51%, solving the problem.
After confirming the solution, we made some duct and temperature controls modifications, and the humidity and mold problem was solved.
Tuesday, March 9, 2010
DESIGN/BUILD GONE WRONG
The design/build method of project delivery is popular because it is seen to save both time and money in the construction process. In many cases, when ethical contractors are employed, results are favorable. There are times, however, due to either cost or schedule pressures, the owner is unsatisfied with the product.
I have been called to consult on some of these. In almost all projects, a professional engineer is hired by the contractor to execute a design, as stamped drawings are required to obtain a building permit. In the best of all worlds, the contractor and engineer, working together, can create a design that provides an excellent, cost effective solution.
Watch out, however, for the design/build solution that responds mostly to cost pressures. Most of my litigation assignments involve in some way a design and implementation that cuts corners to save money. Some that come to mind include a lack of control valves, skimping on insulation, undersizing of pipe and ductwork, and inferior temperature control systems.
When using the design/build method, it is alway a good idea to employ an independent engineer to review the proposed design to make sure that it delivers what is required. Poor system performance is no bargain.
MOLD FORMATION
It is not uncommon in new buildings to see the formation of mold and mildew. How can this happen?
Over the years I have observed the mold formation phenomenon resulting from a variety of causes, but generally all come down to poor construction technique. In one case, the staged drywall was allowed to get wet. In another, lined ductwork was left out in the rain before installation.
In each case, the construction materials were allowed to get damp or wet. After installation, the air conditioning was turned on, and the materials were exposed to low dewpoint temperature air. The result: dampness became liquid water, and spores grew into mold.
It is not uncommon in new buildings to see the formation of mold and mildew. How can this happen?
Over the years I have observed the mold formation phenomenon resulting from a variety of causes, but generally all come down to poor construction technique. In one case, the staged drywall was allowed to get wet. In another, lined ductwork was left out in the rain before installation.
In each case, the construction materials were allowed to get damp or wet. After installation, the air conditioning was turned on, and the materials were exposed to low dewpoint temperature air. The result: dampness became liquid water, and spores grew into mold.
Monday, March 8, 2010
WINDOW CHOICE AND MOLD/MILDEW
Most know that today's double pane windows save energy. But other factors contribute to the satisfactory performance of the window, including whether the window frame creates condensation.
In cold climates it is important to install a metal frame window that is "thermally broken". This means a frame with physical discontinuation between the exterior and interior. If the frame is not thermally broken, that is, continuous from cold outside to warm inside, the inside of the frame will be cold. That cold surface will cause condensation of airborne moisture in the space. Eventually, that "sweating" on the frame interior will cause the formation of mold and mildew.
Thermally broken metal frame windows should be installed in any climate where the winter temperature regularly falls to below 55 F.
Most know that today's double pane windows save energy. But other factors contribute to the satisfactory performance of the window, including whether the window frame creates condensation.
In cold climates it is important to install a metal frame window that is "thermally broken". This means a frame with physical discontinuation between the exterior and interior. If the frame is not thermally broken, that is, continuous from cold outside to warm inside, the inside of the frame will be cold. That cold surface will cause condensation of airborne moisture in the space. Eventually, that "sweating" on the frame interior will cause the formation of mold and mildew.
Thermally broken metal frame windows should be installed in any climate where the winter temperature regularly falls to below 55 F.
Wednesday, February 24, 2010
WHERE DID THAT MOLD COME FROM?
Mold and mildew is the result of liquid water coming in contact with mold spores. The spores are everywhere! In an air conditioning context, the liquid water results from airborne moisture coming in conact with a surface colder than the water vapor temperature. Remember the "sweating" of a cold glass of iced tea in the summer? The surface temperature of the glass is lower than the vapor temperature of the air, resulting in condensation. If window frames are damp, you probably have the wrong type window frame.
Mold and mildew is the result of liquid water coming in contact with mold spores. The spores are everywhere! In an air conditioning context, the liquid water results from airborne moisture coming in conact with a surface colder than the water vapor temperature. Remember the "sweating" of a cold glass of iced tea in the summer? The surface temperature of the glass is lower than the vapor temperature of the air, resulting in condensation. If window frames are damp, you probably have the wrong type window frame.
GET A CARBON MONOXIDE DETECTOR
It's simple, its cheap, and it could save your life. Anyone with a natural gas furnace needs one. Heat exchangers in gas furnaces wear out, and crack. Out comes a product of combustion called carbon monoxide. It is odorless, but lethal. Especially if your furnace is over 20 years old, you are at risk. People go to sleep and never wake up. So...head down to your home improvement store and get one, they run about 20 bucks.
It's simple, its cheap, and it could save your life. Anyone with a natural gas furnace needs one. Heat exchangers in gas furnaces wear out, and crack. Out comes a product of combustion called carbon monoxide. It is odorless, but lethal. Especially if your furnace is over 20 years old, you are at risk. People go to sleep and never wake up. So...head down to your home improvement store and get one, they run about 20 bucks.
Friday, February 19, 2010
WHY ARE MY WINDOWS LEAKING IN THE WINTER?
My windows are leaking, but it isn't raining! Well, your windows are probably not leaking, but rather are "sweating". The moisture you have observed on the windows is actually condensation. This results from cold window frames in contact with moist indoor air. If the windows are non-thermally broken, the metal is cold and will cause condensation. Should you not be able to replace the windows, crack them a bit to let in some dry air. It will cost energy, but you will get fresh air and skip the cost of window replacement.
My windows are leaking, but it isn't raining! Well, your windows are probably not leaking, but rather are "sweating". The moisture you have observed on the windows is actually condensation. This results from cold window frames in contact with moist indoor air. If the windows are non-thermally broken, the metal is cold and will cause condensation. Should you not be able to replace the windows, crack them a bit to let in some dry air. It will cost energy, but you will get fresh air and skip the cost of window replacement.
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