Forced-Air Systems
How do you deliver heating/cooling to each area of the building? The majority of systems rely on air as the delivery tool. We call these systems "forced-air" systems, as we are forcing the air through ductwork, with fans or blowers, to deliver air to each area of the house. When moving air through ductwork, the integrity of the ductwork is of great importance.
The key factors of ductwork integrity are:
- Air tightness - If the ductwork leaks, polluted air can be sucked into the duct from unpleasant spaces (crawlsapces, attics, garages, floor systems, building cavities, etc.). These leaks can also cause conditioned air to leak out of the house, sometimes increasing liklihood of condensation issues.
- Material - What is your ducting made of? Is it made of fiberglass? Maybe metal? Is it lined with fibrous insulation? All of the air in your home circulates through the ductwork, many times each day. It is very important that the duct material be clean, as well as cleanable. Duct replacement and/or cleaning is a frequent part of our retrofit jobs.
- Sizing & Installation - Duct sizing affects the ability of the blower to push the correct amount of air to each location of the building. If the duct is too small, then it restricts the flow of air, making it difficult to keep some areas of the building comfortable. Sizing is also related to NOISE issues. If too much air is being forced through a duct that is too small, you'll be able to hear it rushing out of the register. Noisy ducts are a noticable symptom of duct sizing and/or air-distribution issues.
Balanced Airflow & Pressure - Because your house always holds the same volume of air, the very act of moving it from one area to another (forced-air system) can create changes in pressure from room-to-room and/or between inside and outside. As was discussed in the "airflow" section of our "Building Science" section, when a room is under negative pressure, it wants to suck air in to equalize the pressure. This "suction" is to be avoided, as sucking in air from the attic, the crawlspace, the garage, or the outside is not only inefficient, but also brings in pollutants. The graph (RIGHT) shows that the average infiltration rate TRIPLES when interior doors are closed as a result of the unbalanced nature of the air distribution.- Insulation - Duct systems should be insulated to prevent the gain/loss of heat through the walls of the duct system. The presence of insulation also reduces the liklihood of condensation in cooling months.
Water Systems
Water is another primary delivery system for transporting heat to areas of the house. Water is heated and then circlated through pipes using a pump. Pump selection is critical, as you don't want to have a pump that is too large (expensive) or too weak.
Water systems generally use one of two methods to transfer the heat from the pipe to the space requiring heat. The first type is a wall/floor mounted radiator (photo RIGHT).
The other primary transfer strategy is through a radiant floor system, where the entire floor becomes the transferer of the heat. This produces a very even heat throughout the entire space, virtually eliminating cool areas.
There are a number of ways to incorporate radiant floors into a home. The required water temperature varies, depending on what type of flooring system is involved. Generally speaking, the lower temperature systems will operate more efficiently, requiring less fuel.
Water system lend themselves to entertie with both solar hot water systems and ground-source heat pump systems.
