One room's hot, one rooms cold. Where to investigate?

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Permalink Reply by Judi Lyall on December 30, 2010 at 10:18am

I Like reading these questions. I think it is just the flow to that room that needs to be adjusted. I live in a home similar to this. In the summer both my HVAC units are set at 79. I have my thermostat  programed for our usage thruout the day. We work out of our home.  My upstairs unit goes on more often, due to it is warmer up there, but we are never up there during the day. Downstairs rarely goes on at all. I have a delemia there. I thought of turning the thermostat higher upstairs. In the winter, the thermostat is on 69 downstairs goes on and our upsatirs is set at 65 and while we sleep we perfer it cold and than at 4am the heat kicks in, so when we wake up it is comfortable. Please tell us what you found as the problem so we can learn from this. Thanks for sharing.

Judi Lyall

SHE BUILDS GREEN 

Permalink Reply by Sean Lintow Sr on December 30, 2010 at 7:58pm

In most cases, issues like this require a real good HVAC guy that knows his Manual J, S, T & D. Are the ducts properly sized for that area, sealed up or disconnected (check CFM of air flow coming through vents for a quick check) You might also check out a zoned ducted system where each room has a thermostat in it - works great with multi speed units

 

Quick gut check says, IR pictures might show one wall with no insulation or not enough if next to an attic, or if it is over garage no insulation between garage and room

 

Permalink Reply by Joel Greenberg on January 18, 2011 at 4:28pm

I've decided to recommend an HVAC guy that's NCI certified to do air balancing. 

 

I've also recommended they install jumper ducts in the bedrooms, but only if they need it after air balancing.  Two clues: a) one of the bedrooms was more comfortable when they left the door open over night, and b) the master bedroom door would close all the way if you closed it 80%.

 

As for insulation, they have it in the walls and the ceiling, but thermal imaging shows the typical thermal bridging across the top plate.  Insulation teams don't like so much to scooch close to the eves, so they don't end up covering the top plates of the walls.  See below.

 

Before blower door:

After blower door:

 

I think air balancing will solve most of their problem.  Once the HVAC system and duct work is tuned up and running like a top, they can decide on other measures, but they may not need to.  Air balancing may solve the problem enough.

 

Permalink Reply by Bob Mariani on December 22, 2011 at 1:06pm

The wisps you see in this image indicate air leakage causing room to be cold.  The tthermal bridging would not flare out like this.

Permalink Reply by tedkidd on June 30, 2011 at 9:30am

If the envelope is tight it may be an equipment oversize issue.  I always ask if equipment ever runs continuously.

 

Like many building science truth's that are intuitively backwards, undersizing equipment is better than oversizing.   Oversized equipment short cycles, satisfying downstairs but delivering warm air upstairs because the duct doesn't have a chance to cool. A good way to tell that equipment is oversized it check humidity levels.  If RH is higher than outdoors, you are cooling too quickly.  

 

If the envelope is messed up, this really can't be properly fixed until envelope is fixed.  In winter heated air goes up on it's way out, somewhat correcting load to distribution imbalance's.  In summer cold air dropping sucks superheated attic air into upstairs, and poor insulation allows it to radiate, exacerbating imbalance.