Floor or ceiling register placement advice

[David Edens]

Occasionally I get an advice ? from a client on an older house that does not have central HCAC. Should the vents go on the floor of the crawlspaced house or in the attic of the 1 story house if a central system was installed. I try to defer the advice to an HVAC tech but was wondering if you had and thoughts. Also, when is the breaking point for having a second unit service upstairs instead of a single system for both floors?

[Tony Mount]

David, I found that it is easier to put the unit in the attic if there is room, because once you put one in the crawlspace you can not service the plumbing under the house because the installers use the access to run the duct starting from the farthest point working back to the unit.

[Patrick Norton]

David,
I would install the ductwork in the crawlspace (dry and sealed) and heat from the floor. Heating from the ceiling is not desirable. If it was basically air conditioning mostly that may be fine from the ceiling.

[Jerry Peck]

Also, when is the breaking point for having a second unit service upstairs instead of a single system for both floors?

Basically preference of the owner / contractor / HVAC company designer.

You can have one large unit cooling everything, however, you get more control if you have separate units controlling separate areas, such as: upstairs or downstairs, bedrooms or living areas, master bedroom or other bedrooms - all depends on how you want it split up for convenience uses.

[Gunnar Alquist]

I know a local HVA/C contractor that will not install ducting under the house (unless above the ceiling is completely inaccessible. His reasoning is that furniture will block airflow from floor registers. With many of the new furnaces, the temperature difference (interior air vs. heated/cooled air) is closer and the blower operates for longer periods of time, resulting in less stratification of air temperature. In addition, crud falls into floor registers and not into ceiling registers. I am not entirely convinced about the air distribution, but he says he has documentation. Seems to me that as long as the ducting and registers are appropriately sized and balanced, either way should work fine. If Tennessee is more of a cooling climate than a heating climate, the ceiling registers would probably work out better overall.

[Jim Robinson]

I have ducts in the ceiling (actually a soffit near the ceiling). I can guarantee that I would never buy another house with that installation. It just doesn't warm up very well during cold weather. I checked the floors with my laser thermometer. 50 degrees when we wake up in the winter time. It takes almost all day for the floor to warm up significantly. That's not saying that forced air in the floor would warm up the flooring either, but I would not put ducts in the ceiling for forced air in my house.

However, since this is an older house, I am assuming it already has some type of heating system. In that case, if it is just central air, the ceiling would probably work just great. I probably would put the ducts in the ceiling if it was AC only, and some other (hydronic?) heat system.

[Gunnar Alquist]

Jim,

You might want to have your heating system evaluated by a licensed/qualified/professional HVA/C contractor and corrections/repairs made, as needed. ;)

[James Duffin]

Most of the newer two story houses I see these days have a gas pack or crawl space unit for the first floor with floor registers and an attic unit for the top floor with ceiling registers. Both seem to work fine if designed and installed properly.

[David Abrahar]

Hi,
I am new here and have a question relevant to this topic.
There is a house in North Toronto, Canada that had radiant (radiator) oil heating. No crawl space. The system was damaged due to freezing and needs to be totally replaced.
Would you guys recommand a radiant system as before, A mini-duct hi-velocity, or a forced air system.
To place a forced air or mini-duct, the registers have to go to the ceiling of first floor and floor of Second floor.
Cost is almost the same for all systems. The system should work on oil, propane, or electric. More difficult to place ducts, than water pipes.

Cooling is not an issue as the property is on a lake.
The main question is a forced air with registers on ceiling or a radiant system?
Thanks

[Jim Robinson]

Toronto - no question I would pick a radiant system.

[Ted Menelly]

Occasionally I get an advice ? from a client on an older house that does not have central HCAC. Should the vents go on the floor of the crawlspaced house or in the attic of the 1 story house if a central system was installed. I try to defer the advice to an HVAC tech but was wondering if you had and thoughts. Also, when is the breaking point for having a second unit service upstairs instead of a single system for both floors?

The attic with the vents in the ceiling is what the general consensus of the HVAC contractors I have talked to. I have been in to many crawls where duct work hinders access to areas and damage can be done more easily. Moisture and ventilation is also much more difficult to regulate in a crawl

My personal choice would be the attic with the unit in a closet in the home. R9 flex duct, proper attic ventilation and a return duct from every room with a door.

I lived in the colder climate of Mass, the hotter more humid climate of Florida and now the hotter dryer climate of North Central Texas. I have built and or remodelled homes in every state. Actual supply vent placement would be different in colder or hotter climates. Return duct placement is also different in hot to cold climates and that depends on the philosophy of individual HVAC techs.

Just my thoughts

Ted

[Robert Dalga]

Both the attic and/or crawlspace are unconditioned areas, however AC ducts running thru the attic would be less efficient than in a crawlspace (assuming identical installations) due to the temperature differential (that is...attic being much warmer during the summer months). Nevertheless, ducts should be well insulated regardless of either location. Opposite would be true for heating season. I'm a firm believer that all ductwork should be installed in 'conditioned' areas for maximum efficiency.

[Jerry McCarthy]

I would argue that heating vents should be located in the floor, especially under a window and cooling vents in the ceiling. (cold air descends, hot air rises) However, that's the ultimate system and commonly in a split-system I'd still pick the floor for my outlets, but then again the region would most likely dictate locations. Wait! Actually the ultimate heating system is hydronic – bar none!

[Ted Menelly]

Both the attic and/or crawlspace are unconditioned areas, however AC ducts running thru the attic would be less efficient than in a crawlspace (assuming identical installations) due to the temperature differential (that is...attic being much warmer during the summer months). Nevertheless, ducts should be well insulated regardless of either location. Opposite would be true for heating season. I'm a firm believer that all ductwork should be installed in 'conditioned' areas for maximum efficiency.

Yeah, what you said About the ducts and equipment in conditioned spaces.

I have lived in three different climates. Hot and humid, hot and dry and oh yeah just to hot and humid in the summer and to damn cold in the winter.

Washing the walls in the winter pushing it up keeps cold drafts of your lower portions. Blowing against the wall from across the room to the outside wall with the cold air in the summer.

Radiant boiler fired floor heat it great. Just keep the hunidifier on for your wood floors.

The part about the crawls. I have seen way to many ducts in way to many miserable crawls to agree to any duct down there. Half I've seen are damaged or damp problems and so on.

Did I say I hate crawls. Dirty, damp half the time, bugs and lions and tigers and bears, oh my.