What kind of test could be preformed, when a home owner says that the Master bedroom really doesn’t warm up to a comfortable level?
This bedroom is the farthest away from the heat source, 80,000btu, 3000 sf house. There are 3 heat registers in the bedroom.

This is a warranty inspection, 11 month.

This problem is way too common!!!

Have walls and attic been checked for insulation?

Is the heat source at one end of the house and the bedroom at the other? If so, it’s a bad design decision to begin with!!! But It could have been corrected/improved by oversizing ducts running to the room a bit, sealing the duct joints, and insulating those ducts to conserve heat.

Check heating system plans to ensure that designed duct sizes were used.

Check/re-balance air flows to rooms. Ensure that the dampers/registers to the bedroom are wide open. Damper down airflows to the rooms closest to the source; this forces more warm air to the other rooms and may not affect comfort in these closer rooms. Keep doing this to see if airflow and heat supply to the bedroom increases significantly. Do not shut off any airflows!!

More technical:

-Calculate heat loss for the room at outdoor design temperatures for the area (this should have been done by the designer/installer of the heating system and may be available from them)

-Again check installation against design.

-Check airflows and temps using an air balancing technician. He will use a flow hood or velometer to get air velocities and then calculate flows for each register. Then using the air temps it can be calculated how much heat is getting to the room.

My first red flag I have a problem with that size furnace on a 3K house blower motor and blower wheel does not have the capability of moving the proper CFM regardless of the insulation.

I concur.

80,000 BTU’s for 3,000 sq. feet? Are you sure the BTU’s are 80,000?


I thought that at first also but only one room has the problem.

Some of today’s better built homes with highre insulation levels, good airtightness, Low “E”/Argon gas fill windows with “warm edge” spacers will have design heat losses down in this range or lower.

It would be interesting to find out how long the furnace is running on the coldest days of the year. If it’s only running 30-35 minutes/hr, then there’s still lots of capacity to heat that room but the duct design has been botched or there’s been a bad installation.

ps: Just checked the local yearly degree days- approx 5000-5200- not too severe. I’m living in 7400 DD or so and might consider that furnace to be a bit small for that size of house here. Couldn’t easily find the design low temp for the area…which would, along with the heat loss characteristics of the home, really determine the furnace size.

I’ve got a similar problem in my home. Only I’ve got 120,000 BTU’s and am right over the furnace… Our BR only gets warm if we leave the door open…Any guesses? Yep, no cold air return.

80,000 BTU for 3000 sf is pretty small, but I would think it would just run all the time.

This may be way to obvious but when I get the same question the first thing I do is check my thermometer to see that the temp is coming out of the vent in question. 100-110 degrees (thats what I usually see here) and then make sure all them are the same or are close to the same.
If that one is not then I would go to the crawl space and check the ducting to see if there is debris in the duct work. You would be surprised how I often I find this to be the case, 2x4’s, and misc wood debris not to mention water in the ducting:shock: . I would say that 1 out of 20 homes will have standing water (usually new construction ). As far as the previous posts I agree this is just something I check for as well. Good luck.

If the furnace blower is not properly sized it will not build static pressure within the duct to provide proper CFM at the most remote register I generally tried to have between 300 and 400 CFM on a residential unit at each register preferably at the 400 level. If you have an undersized blower the air just looses itself within the duct. Air flow is just like water flow it takes the path of least resistance


It would be nice if they had a smaller measurement tool to check CFM’s.


I basically work my temp readings the same way. If a register isn’t supplying adequate heat (compared to others on the same level), I’ll find the problem in the basement somewhere. Ducts are usually not connected or insulated, kinked, or too long.

There is fits in the palm of your hand will try to look it up for you still writing todays junked up house.

Here’s a page with a few vane anemometers. I said velometer (another velocity measuring tool) this AM…been out of the air balancing field for 16 years now!!!


David Professional equipment also has anemometers but a little pricey.


I have one of these somewhere.



I think alnor makes a smaler one too.

Not too many people would know of Alnor (or Shortridge, for that matter). What background do you have to know of this company?

I just found some great deals HERE.

I’m going to go above and beyond and start to do these tests on HVAC.


If I were to purchase this one, what readings should I be obtaining (approximately) on HVAC registers?

I bought a whack of equipment through these folks in 1990. They had some of the best prices around then. haven’t checked today’s prices though.


I just did the research for ya. They are not as cheap as the link I posted.

Busboy at a Lobster house. :smiley: