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2 Answers

Water Heater Backdraft

I have a gas-fired natural draft water heater and furnace in our 15 year-old home in Lincoln, NE (zone 5). After doing some attic air sealing a couple years ago, our leakage rate dropped to 1.5 ACH50. I did a combustion backdraft test and everything was fine.

Asked By Derrick Krienert | Dec 31 16
5 Answers

Bathroom vent design

The upper floor of my house has a cathedral ceiling constructed of 2.4"x6" cedar planks. I'm putting a new roof on it this week with foam board under the metal so it will finally be insulated. One detail in the project is how to replace the bathroom fan. Currently, it is an exterior unit that draws through a 6" duct. It draws plenty of air, but also leaks heated air. I'm planning to get a new rooftop unit so that I don't have to build anything inside:

So, my questions are:

1) Is there some kind of (passive preferably) damper that could be put in to reduce air loss?

Asked By Robert Hudson | Dec 26 16
14 Answers

Radiant heat loss

If I understand manual J correctly, heating load calculations do not consider radiant losses. I am trying to figure out why that is ok. It seems like a house that is out in the open (not surrounded by trees or other buildings) would lose substantial heat by radiation on a clear night. Is radiant heat transfer small enough that assuming the surface is at the ambient air temperature is a safe simplification?

Asked By Reid Baldwin | Dec 23 16
5 Answers

How efficient are commercial water heaters when used in a single residence?

Commercial water heaters receive a Thermal Efficiency, rather than an AFUE rating. TE does not convert to AFUE as the testing protocols are different. Thermal Efficiency is a snapshot reading at steady state and AFUE is a seasonal rating that takes into account cycling and other losses. If a commercial water heater was tested using the AFUE protocol, the AFUE would be substantially lower than the TE figure. Here are the questions... First, is it assumed that a commercial unit in a commercial setting is under almost constant demand, and therefore the cycling losses are inconsequential?

Asked By Melissa Ames | Dec 20 16
13 Answers

Mini-split design possibilities... suggestions appreciated

Update to my prior thread where I was hemming and hawing about the right strategy for HVAC.

House summary:
North end of Climate Zone 5
All-Electric. No gas. No propane.

Asked By Dave De C | Dec 12 16
21 Answers

Need advice on air intake changes for backdrafting wood stove...

We recently built a "pretty good" 1200 square foot bungalow (insulated slab on grade, no basement) in zone 7/8 (Canada) with in-floor heat (hydronic, electric boiler). It's very tight. Last winter we were unable to use our small wood stove much because at the end of each burn, as the fire was dying down, we got backpuffing from the chimney near the ceiling (this is our wood stove...

Asked By Beth Turner | Nov 4 16
5 Answers


I am building a net zero house, 2000 SF, 2 stories in Mystic CT. It has 2 full baths, heating and cooling by 2 mini splits, ventilation with an HRV, range hood in kitchen (not sure if it will have makeup air capability). Most of what I have read says to exhaust from bathrooms, laundry room and maybe the kitchen. Supply to bedrooms and living room.

Q1 - Will the ventilation system blowing air into the bedrooms prevent conditioned air from getting into the bedrooms?

Asked By Courtney McCracken | Dec 12 16
6 Answers

Hypothetical daily cost comparison (minisplits vs. electric resistance)

I'm trying to help steer a colleague towards heat pumps since his old equipment is in need of replacement, and am trying to determine some hypothetical comparison numbers. No heat loss calculation has been done, but that is besides the point for this comparison since it would be a fixed number specific to his house, and not the heating equipment. Heat loss could be 20,000 or 100,000btu, but i am using 30,000 for this example. He currently heats with wood and electric resistance backup...(but that is not the point below)


Asked By Ryan Magladry Ottawa, Ontario | Dec 14 16
8 Answers

Is this a valid way to measure heat load?

Our manual J calculation said that the heat load of the house is about 30K at about 65 degree delta T. (It was more precise than that but I don't have the report handy, so I am going from memory.) I am hoping to confirm that the actual load is not too far away from that before we get into really cold weather.

Asked By Reid Baldwin | Dec 5 16
4 Answers

How do I get rid of a LARGE AMOUNT of attic moisture?

I bought the house I grew up in that was built in 1952 24x30. 1972 an addition was added making it L shaped. I had central AC installed 2016. The installer did a terrible job of installing the metal boots in each room and there was no stopping airflow around them, not properly insulated, and insulation was not packed back around them. For a year and a few months this was the condition. Then my daughter moved in and was washing cloths and hanging whole loads of laundry in the house. I also had house pressure washed.

Asked By Scott Hill | Dec 10 16
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