I’ve inspected several new construction houses over the last few years with the following: 2 story house, 2 systems, 1 system serving upstairs and 1 serving downstairs, both returns in the second floor ceiling, no return downstairs. I’ve had an HVAC guy I respect tell me that the downstairs return needs to be located downstairs otherwise the occupants will have a hard time being comfortable. All the inspections have either been pre-drywall or pre-movein and I’ve not gone back and contacted the owners to find out how it worked out.
Opinions? Have you found that having both returns on the second floor does not work out well?
The other issue that gets noted is one stat upstairs and returns and T-stats in bedrooms or other potentially isolated locations.
Doors are closed and the rest of the zone suffers, unless jump ducts are installed.
Under-cutting doors by 1-2" is not sufficient and usually looks like hell when the builder or homeowner tries to resolve an inadequate incorrect install.
I love the new homes where you turn on the systems and doors start slamming shut.
Sounds logical, but I’ve seen returns upstairs and thermostat’s downstairs. Also seen returns way down the hall and thermostats in the master bedroom 40 feet away. Usually these are new homes.
I don’t call out design deficiencies because I don’t have to and because I’m not a licensed HVAC contractor and am therefore not qualified, but I often tell the client that they should consult with the builder about it during the walk through.
So long as it doesnt get cold in Texas!!! both returns in the 2nd floor will work in the summer, but is not right!
You will find the problem surfacing in the winter months as the hot air rises (and will short cycle) without heating the lower floor. You can’t get cold air upstairs to the HVAC unit without a return at the floor.
Joe, I do call out design deficiencies when they’re fairly obvious, such as with a two story house located in the blistering S.F. Valley that has a southern exposure, single-glazed windows, and a return-air on the ground floor. I warn them that they may not be entirely satisfied with the air-conditioning on the second floor during the height of the Summer, and invite them to get a second opinion. People tend to get grumpy when they’re not comfortable, and in Southern California they sue, demand a new system and a cool million in punitive damages.
Unlike a lot of things in HVAC, the location of return air grills is definitive.
If you can not remove the air to be treated from the location and process it in an HVAC machine, the system will not work.
Hot air rises and cold air falls. When you have a two story house with one air-conditioning system and there is not a return on both floors, or in this case are both located on the same floor, it simply will not work. The duct system can only be designed for heating or cooling. It will not work efficiently for both. Sometimes we can “get by” with marginal applications, however the case in question is not a marginal case.
The only way one HVAC system can adequately perform in a two-story house is if a zone control system is installed and there is a return register on both floors. If you do not have an automatic controlled zone system, then seasonal campers must be installed that are manually change between winter heating and summer cooling mode.
It is seldom considered, however balancing the return air is as critical to performance as balancing the supply air.
Air is a fluid. It contains a considerable amount of moisture which does not like to change temperature readily. Blowing cold air into a hot room does not change the ambient temperature of the room efficiently. You cannot remove the moisture from the air by just blowing cold air into it because you must move the air through the HVAC system to remove it.
Heating systems are generally less critical if a return is located on the lowest floor as cool air is removed and hot air rises to the second-floor (just leave the doors open). So it is less noticeable in the winter than it is in the summer. In southern locations cooling is the most important function of the HVAC system, so the system should be designed cooling. The heating system seems to get by without any complications in most cases.
