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ENERGY EFFICIENCY AROUND THE HOUSE


Everyone needs a chance to VENT with Craig Hendrickson


Residential Energy Auditor K


eeping an attic ventilated is one of the most important things you can do for your home. A well-ventilated attic will keep your home cooler in the summer and help re-


move damaging humidity year round. Experts tell us the best way to ventilate an attic is a combina-


tion of a ridge vent and several soffi t vents. T e ridge vent acts as the exhaust while the soffi t vents act as air intakes. T e air enters through the soffi t vents, mixes with the air in the attic, and quickly is drawn outside by the ridge vent. T ere are no moving parts or motors to malfunction. Nat- ural physics is at work to move the warmer air out. With this natural fl ow of air, moisture is also pulled out of your attic (roof vents located near the top of the roof can be used instead of a ridge vent). To calculate the ventilation needed in your


attic, use this formula: square feet of attic fl oor divided by 150 results in the number of square feet of ventilation needed. Half of ventilation should be from the soffi t vents and half the ridge vent, so divide the resulting number by two. For example, a 1500 square foot attic ÷ 150 = 10 square feet of ventilation ÷ 2 = 5 square feet (5 sq. ſt . in the soffi ts and 5 sq. ſt . in the ridge). Keeping this ratio as close as possi- ble will ensure the best air fl ow. Next, consult with the manufacture of the vents to determine how much ventilation the diff erent types of vents provide. Some vents have the amount of air (net free area) displayed on the fl ange or label.


When installing a ridge vent check with the manufacturer’s


instructions on the amount of sheathing to cut away from the ridge of the roof to allow the vent to work at its full potential. If installing ridge and roof vents on homes with multilevel roof de- signs, it is important to locate them at the highest point possible and avoid placing them at diff erent heights. As you install soffi t vents, pay attention the attic


insulation does not cover the air passage. Consider using raſt er chutes to keep insulation out of the air way, between the soffi t vents and the attic. Soffi t vents should be installed evenly around the home, not all on one side. T is will reduce the possibility of hot spots. Over the years, I have heard a few complaints


Louvered roof vent


Cut-away of a ridge vent with baffl es and a fi ber fi lter.


about ridge vents allowing powdery snow to blow into the attic leaving mounds of the white stuff behind. T e snow will eventually melt and leave a damaging mess. I did some research on how folks up North handle this problem since they have much more snow than in Oklahoma. I found the vents are more complex. T eir ridge vents have baffl es that slow the blowing snow and some also have fi ber fi lters that trap most of the icy powder. T at’s good news. T e better news is some of our hardware and lumber stores are now carrying these ridge vents. Concerns that fi ber fi lters trap dirt and become


clogged are easily resolved by blowing out the dust with an air compressor. I have not experienced this, but would rather blow out the dirt every few years


than shovel bushels of snow from the fl oor of my attic.


There is a relatively new concept called a ventless attic. It is gaining popularity in the northern and eastern regions of the United States. The procedure calls for spraying foam insulation on the underside of the roof sheathing. This also includes spraying over all attic vents to seal the attic from the outdoors. You are, in actuality, making the attic another room. You do not insulate the fl oor of the attic at all. To keep moisture at bay, a conditioned air source is introduced into the attic (usually from duct work already in the attic) and you can do something as simple as leaving the attic entrance panel ajar to act as return air back to the climate control system. I have been in two ventless attics this summer and both were very cool compared to a conventional attic. A ventless attic produces positive benefi ts such as: no insulation needed on the fl oor of the attic which allows the entire fl oor to be fi tted with fl ooring; the attic should stay at a pleasing temperature to allow you to store more delicate items; if any part of the climate control system is housed in the attic, it will be able to operate with less stress and better effi ciency due to the improved temperature; and, if the duct work is in the attic, it will deliver air to the source ducts with better effi ciency (the return air ducts will also be more effi cient). It is important to note that all bathroom, kitchen, and plumbing vents that pass through the ceiling must exhaust through the roof to the outside.


August 2013 - 9


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