Posted on Sep 18 2013 by This unvented conditioned attic has spray foam insulation at the roofline. Although not the same house as the one discussed in the article, this attic does indicate a similar problem: atmospheric combustion appliances in the house. This particular attic also has a blatant code violation: the installers sprayed foam insulation directly on the metal flues. Earlier this year I got a question about a home that had spray foam insulation in the attic. There's nothing unusual about that. A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits. But then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents. A case of incompatibility The attic you see in the photo here is a different home, but it does have one feature in common with the house I'm talking about, besides the spray foam. If you look closely, you'll see two exhaust flues on the left side of the photo.

(You'll also see another safety hazard and code violation: The installer sprayed foam directly on the metal flues. used heating and air conditioning units for saleYou should never do this!) ac unit filter replacementThose metal pipes indicate to the trained eye that this house has atmospheric combustion appliances.best ac units 2012 In the photo here, the furnaces were down in the conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. , but in the house my friend asked about, the two furnaces were in the attic. They also were of the atmospheric combustion type. See where I'm going with this yet? The spray foam contractor on that job saw the two atmospheric combustion furnaces in the attic and knew they needed combustion air from the space around them.

If he had sealed up the attic completely, where would the furnaces get combustion air?That's why they didn't seal the gable vents. Now when those furnaces run, they can pull in the combustion air they need through those holes. Creating a Conditioned Attic GBA Encyclopedia: Vented or Unvented Attic? Sealed-Combustion Appliances and Hot Tub Parties Combustion Safety and the Worst-Case Depressurization Test Q&A: An exterior air intake for combustion?If the homeowners are getting spray foam on their roofline to make the home more airtight, why would they leave big holes to the outside? A house is a system It's nice that the spray foam insulation contractor recognized the need for combustion air in that case. In many, they don't get that far. Whether you're building a new home or retrofitting an existing home, though, you've got to remember that the hip bone's connected to the thigh bone; or, as we say in building science, a house is a system. Newer homes have to meet building codes that help prevent this problem.

If there are atmospheric combustion appliances inside the building enclosure, the HVAC(Heating, ventilation, and air conditioning). contractor is required to install vents that are supposed to bring combustion air into the room where the appliances are located. If the atmospheric combustion appliances are located in a vented attic, the building code doesn't require those vents because the appliances are already located in a well-vented area that is connected to the outside. But if you move the building enclosure to the roofline with spray foam insulation, where will the combustion air come from? Whether the home is old or new, however, anyone considering spray foam insulation would be wise to ask this question: What impact will encapsulating the attic have on the HVAC system(s)? This question applies to encapsulated crawl spaces as well. If you have atmospheric combustion in the home now, it might be best to wait and do the spray foam after you've replaced the old equipment with sealed combustionCombustion system for space heating or water heating in which outside combustion air is fed directly into the combustion chamber and flue gasses are exhausted directly outside., power-vented, or direct vent appliances.

If the house isn't built yet — or at least doesn't have the HVAC equipment installed yet — make sure there are no atmospheric combustion appliances going inside the building enclosure. Remember: A house is a system.You can follow him on Twitter at @EnergyVanguard. † Keep in mind that passive vents may not be the answer. My friend David Richardson, an instructor with the National Comfort Institute, likes to point out that the high-low vents required by code don't always do what they're told. “The issue is it's a two way street for airflow,” he says. “It's common to see combustion air ducts and grilles functioning in direct opposition to their original design intent.”Signs Your Air Ducts Need Cleaning Keep your ducts in a row. Have you noticed little wisps of dust puffing out from an air duct every time you turn on your home's heating ventilation and air conditioning (HVAC) system? Have you seen dust or pet hair trapped in a vent? Is there dust coating the grill on the return air registers?

These might be indications that your home's duct work might be due for a through cleaning. Inside your HVAC system, fine dust collects on air duct surfaces, vents, motors, and coils. Flakes of dead skin, hair, and pet dander catch onto the dust, and before too long this process creates a dense, mat-like environment where bacteria, mould, dust mites, and allergens can flourish. Air filters remove most of these from the air stream, but not for all parts of the HVAC system. That's why it's important to periodically check the condition of your air ducts to see if they could use air duct cleaning services Top 5 Dirty Air Duct Indicators 1. Open one of your vent covers and look inside. See if it contains any dirt, debris, or matted dust. 2. Examine the return air registers for dust buildup, particularly if there are thick, fuzzy coatings of dust. 3. Pull out the air filter. If the air filter is clogged with dust, then air flow is being choked off. This lets more dust settle and build up in the return ductwork.

4. Open the furnace compartment. Examine the blower fan and motor for signs of dust as well as the furnace controls. The more dust you see, the bigger the problem you have. 5. Look at the air conditioning coil. (You may need to remove a panel.) If the coil is dusty or has dust clinging to the housing walls, then the air filter hasn't been working properly. Any of these indicators show that your HVAC system and ductwork is being adversely affected by too much dust and dirt. Top 5 Dirty Consequences So what trouble's in a little dirt and dust? There are a number of problems caused by dirty ducts, ranging from increased energy costs to health problems: 1. Dirt and dust restrict your HVAC system's heating and cooling. In the winter, dirt-clogged heat exchangers cannot warm the air as efficiently. In the summer, dirt-clogged condensing coils are unable to cool the air as well. These both increase the HVAC systems run time, requiring it to use more fuel and energy to heat and cool your home.

2. Dirt and dust restrict air flow. Let's say your system is doing a fine job of heating and cooling the air. But if the blower fan or motor can't turn because of dirt or the air filter is clogged with dust, then the system can't effectively circulate that properly warmed or cooled air through out your home. It's still going to run longer and use more energy. 3. The longer your HVAC system operates, the more wear and tear it undergoes. Long run times can shorten the overall life time of HVAC systems, from AC compressors to hydro pumps, burners, and motor bearings. You'll wear out your home's HVAC system sooner. 4. Dust contains not only fine dirt, but also dead skin, pet dander, microorganisms from cat litter (toxoplasmosis), and other particulates such as pollen, mold spores, fungi, and even rodent feces. Left to contaminate your HVAC system, it can become a breeding ground for bacteria, mites, and other pests. 5. Dirt and dust spread quicker in a home with dirty ducts.

No matter how diligent you may dust and clean your home, fine particulate contaminates, including dangerous allergens, quickly flow from room to room to cover tables, smart phones, and children's toys. Top 5 Benefits of Air Duct Cleaning A visit from a professional air duct cleaning service every 3 to 5 years can prevent many maintenance and health problems before they start. Plus, you'll start saving money on heating and cooling: 1. Better and reliable over-all performance from your HVAC system 2. Fewer expensive repairs from wear and tear and longer HVAC system life 3. More energy efficiency, reducing your energy bills 4. Lower likelihood of respiratory and allergy problems 5. Less dust makes it easier to clean and maintain your home's living space Ultimately, cleaning the ducts of your HVAC system is not a do-it-yourself project. And it's certainly not a job for a cheap guy with an air compressor in a minivan, either. A thorough cleaning can only be performed by using industry-standard equipment designed to handle the size and volume of all kinds of homes.