I’m going to be consulting HVAC contractors soon. I wanted get ideas about the problem and how to fix it.
Situation: 2 story town house, situated in high desert. 1 of the upstairs bedrooms gets 15 degrees hotter or colder than the rest of the house. (Hotter in summer, colder in winter.) This bedroom has 2 outside walls. the other upstairs bedroom is affected to a much smaller extent. It has only 1, shaded outside wall.
It has been this way since the town house was built. It has central heat / air located on the (flat) roof of the town house.
So what do you think could be wrong, and how would you fix it?
Well, at a first guess, it sounds like an insulation problem. Putting more power into the room won’t fix it near as well as insulating it better will. To know which kind of insulation would work best I’d need to know more about the structure: are there windows? How well do they close? Something as apparently silly as using a decent weatherstrip (which may need to be changed yearly or last longer) can make a world of difference. What materials are the walls made of? Etc.
I recently got a 5ºC improvement in a house simply by:
applying a weatherstrip to the two large “outside” windows (all other windows are to internal, small yards with glass ceilings)
and silicon where the putty around the glass was cracked or even, for one of the panes, had never been there.
The first thing I would check is the airflow (CFM) at all of the registers (air vents/diffusers) in the house. Maybe a ductwork damper is partially, or fully closed? Any HVAC guy should be able to test airflow.
Is the AC system fully charged with whatever refrigerant it uses.
On which side of the house is the hot room located? S, SW, SE?
Are there windows in the room? Do they leak air? Do they need to be caulked on the outside? Are they double-hung? Do the seals actually seal? Have you considered adding plastic film over the inside of the window?
What type of insulation is in the walls? Have considered adding more?
Yep. I have the same situation. Nothing works like separate zones. But you don’t need separate units. I have one unit, but 2 zones.
There is nothing “wrong” with your system. Hot air rises, and the 2nd story acts as a good insulator (through the ceiling) for the 1st floor. I have R-30 insulation in the ceilings of my 2nd floor, and it’s still hotter than hell (my house faces SW, with almost no shade in that direction) which makes things even worse).
Do you have a Powered Attic Vent installed on the roof? They reduce the heat in the attic, and the electric power used to run the fan is more than offset by the reduced load on the furnace.
Cover the windows with aluminum foil and leave it like that for a few days. Does it make a big difference in the temperature? If so, get the windows tinted with a film that is for heat rejection.
How cool is the air coming out of the vent? How is the airflow? If it’s weak, you may need to have that duct investigated.
Look into solutions in the attic above the room. Check that there is sufficient insulation over that room. Consider adding a radiant barrier to the underside of the roof which gets the most sun (a radiant barrier is a type of aluminum foil which helps reflect the radiant heat of the roof back to the roof rather than letting it into your attic).
I’m not currently in the unit (it’s rented) but we used to live there. I assumed you meant “registers” when you said ductwork damper. Then I looked it up and they are different things. I’ll definitely ask the HVAC guys about this.
The room is in the NE corner. It has 2 windows: 1 maybe 5’ by 3’ and the other 3’ by 3’. I’ll have the seals checked.
This being the high desert I’m not sure of the R number but they’ve got god insulation. (Built in 1999.)
It seems to be a problem with townhouses; I don’t recall this being a problem with two-story single-family houses, though.
I live in a townhouse with a similar problem. The hot bedroom faces due east, so it gets full sun all morning. I’ve fixed it in part by keeping the (room-darkening) shades down until early afternoon. (I do open them in the morning while I’m getting dressed. The light wakes me up, and natural light is great for doing makeup.)
I put a vent “director” over the vent, so it doesn’t spew cold air into the bottom of my bureau. WHY builders insist on putting vents on the floor and in one of the only two possible locations for a bureau, I have no idea.
It is still warmer than I’d like and it’s only June. I’ll be playing with this as time goes on.
And yes, I’ve already played with adjusting the vents downstairs. They’re all almost totally closed.
OK…this might sound a bit eccentric but a possible organic solution is a roof garden if possible. Roof garden - Wikipedia and it would be attractive to look at.
If the existing HVAC system can’t be tweaked to fix the problem, consider installing a ductless ac system for that hot room. That’s a split system where the compressor is outside and the coil and fan are installed in the hot room. It’s the same principle as having a window ac in that room.
While you’re waiting for the HVAC guy, aquire several thermometers. Place one in the hot room, and place the others in various rooms around the house. Increasing/decreasing air flow to one room will change air flow to the other rooms along that same warm-air supply duct.
Maybe you need to add a booster fan to the hot rooms duct. Cold air is heavier than hot air, and harder to move.
You could remove the register (less air flow restriction) from the hot room, and see that that makes a difference.
(Just for clarification - The warm-air duct blows air into a room. The cold-air duct draws air out of a room.) Maybe your cold-air return is blocked or leaking (no longer properly sealed ie less suction). The furnace needs to draw (cold/hot) air out of a room, which allows the furnace to push air (hot/cold) into a room.
You might also find an infrared thermometer useful in locating leaking windows, electrical outlets, doors, floors, and ceilings.
STEP BY STEP BALANCING -
A homeowner is better suited to balance both their heating and air conditioning air flow than a professional simply because they live in the house and can fine tune the balancing over a period of time. A professional will get it basically right, but constant tweaking will make it really comfortable. Remember that any time you touch one single part of the air flow system, everything changes because there is only one air source and any small change redistributes it all – so make a change and live with it for a few days before making another change.
Many years ago an HVAC guy suggested a register fan but also said “you’re robbing Peter to pay Paul”, suggesting that that would just start a game of whack-a-mole.
Another thing he suggested was to put a return air duct in that room. It doesn’t have one. (Also, I’m kind of surprised. In every place I’ve lived, I only remember having 1 return air duct for the entire house.)
Ah-ha. No return air duct. Does the room have a door? (It’s rare, but some don’t.) Is there a larger than usual gap under, or around, the door to allow air to flow out? It becomes progressively more difficult to force air into a room if there’s no egress for the rooms air. It’s like pumping up a football with a very small leak. The air pressure will eventually equalize. Eventually.
Decades ago, a friend of mine was complaining about the temperature at his office always being too hot. He rented one room of a four room office complex with a common waiting area. I didn’t have any tools but I did smoke, so I lit a cigarette and watched the air flow. All of the offices had adequate incoming air, but only one had anything resembling outflow. We then attempted to check the furnace air handler. I say attempted because we could barely open the utility door while the air handler was running. Almost all of the handlers draw was coming from the common area.
He called the HVAC guy, who balanced the system, and everyone was happy. Come to think of it, he never told me what the HVAC guy found.
