Energy Audit: Hot Tubs and Shortcut Return Air Ducts

by:Jiali     2020-08-23
Each home energy audit provides new challenges concerning testing and evaluating the data collected. Learning where this home can save the most energy and lower the utility bills is the objective. Come along with me now and let's have a look at this home.
The thing is, these folks have about $3,500 to spend on energy efficiency and I need to help them decide what up-grades and retrofits make the most sense.
I have connected the old family freezer and the yard-sale, green refrigerator to a Kill a Watt monitor. I will leave the monitor in place several days, I am looking forward to returning to the home so I can gather the data from the monitor about how much electricity these appliances are actually using.
Other Appliances: I find that besides the freezer and green refrigerator, they have 4 more major appliances.
1. The kitchen refrigerator - appears fairly new. A sticker on the outside of the door and a sticker inside the door, both indicate that this refrigerator was Energy Star qualified when it was manufactured. It may not meet current Energy Star standards, but replacing it with a new refrigerator would not appear to increase energy efficiency by a significant amount. The refrigerator is safe, I can't recommend replacement.
2. The dishwasher - is also Energy Star rated. I like the little Energy Star stickers. Dishwasher is safe, can't recommend replacement.
3. The Clothes washer - is a front load, push button model with energy efficiency written all over it. I don't know what happened to the Energy Star sticker, but it should have been there somewhere. I write down the model number and go to the Energy Star website and find that it is listed as an approved Energy Star model. The clothes washer is safe.
4. The Clothes Dryer - matches the clothes washer, they are a set. An electric clothes dryer has a couple options concerning energy efficiency that are important. One is the automatic drying cycle - so the dryer will shut itself off when the clothes are dry, and the other is the exhaust duct. If the exhaust duct becomes restricted, drying time increases and so does energy consumption.
I question the homeowner about drying times and using the auto-dry feature. I look behind the dryer to see if the dryer duct is pinched, damaged, or disconnected. I also go outside and inspect the exhaust hood for lint build up and flapper valve function. All seems well, the dryer is safe.
The Blower Door Test:
I am getting pretty good at setting up the blower door, just takes me a few minutes. I like setting it up in the front door of a home that is in town, it looks like the DEA is performing a drug bust or something. The blower door is a bright red canvas. People have told me later that the neighbors were real curious about what was going on.
Before turning on the fan and sucking air out of the house, I make sure the wood stove door is shut and secure, I close and latch all the windows and exterior doors, and open all interior doors. I turn the furnace off and pull the furnace filter out.
The blower door indicates the home is leaking at a rate of about 3.8 air changes per hour. I notice considerable draft coming from the floor heating registers. Since the recognized healthy rate concerning air changes per hour is 3.5, I realize that I cannot safely air seal the home and make it much tighter. The air coming from the heating registers concerns me, next is the duct blaster test.
The Duct Blaster Test:
The duct blaster takes a little longer to set up since all the heating vents need to be taped and sealed. The heating vent that is under the two ton entertainment center is a challenge, I finally find a large heavy book and slide it over the top of the vent.
In this house, I don't want to forget about the short cut return air duct cut into the side of the hallway wall. It will need to be sealed also. Cranking up the fan on the duct blaster I find that total duct leakage is 480 cubic feet per minute. The 480 CFM is gross leakage, what I really want is net leakage, or leakage to the outside of the home.
By using the blower door and the duct blaster together, I can separate the duct leakage into two parts. I am most interested in the amount of air that is leaking out of the heating ducts and is lost to the great outdoors.
I warn the homeowners that things are going to get a little noisy and a little breezy - I crank up both fans. The leakage to outside the home is 320 CFM. I like this figure, 320 CFM is a significant amount of duct leakage and sealing the heating ducts will save noticeable energy.
Final Recommendations: After putting away all my equipment, I sit down with the homeowners, get out my paperwork, and discuss specific recommendations on how they can best use $3,500 to make their home more energy efficient and more comfortable.
1. Seal the Heating Ducts: Fortunately, this home is serviced by a power company that provides incentives for duct sealing in manufactured homes. I will arrange for a certified duct sealing contractor to seal the ducts in this home and it won't cost the homeowner a penny. A good duct sealing contractor should be able to lower the duct leakage to under 100 CFM.
2. Insulation and Air Sealing: I will recommend that the floor in the two room addition is air sealed then insulated. There is good crawl space under the floor - I estimate this will cost about $650.
3. Addition of a Heat Pump: The lady of the house is having additional problems with asthma. When she has an attack, the wood stove is not used and the electric furnace takes over - this is happening more frequently. With aging, keeping the wood pile stocked is not as much fun as it used to be.
By installing a heat pump, they will have more efficient heating and they will have efficient, whole house cooling. I estimate that adding a heat pump to this home will cost about $2,800.
Well, I am going say goodbye to this house for now. I still look forward to checking the Kill a Watt meters in a few days to see how much electricity that freezer and green refrigerator is adding to the electric bill. The next step will be to schedule the duct sealing and to get a couple bids on installing a heat pump and having the underfloor area sealed and insulated. Feeling pretty good about what I have accomplished, I head on down the road.
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