I am going to remodel my kitchen. Currently there is only one forced air A/C duct in the kitchen in the wall near the floor. This wall will be covered by cabinets as well as all other available kitchen walls. Where is the best place to relocate the only existing duct I have? I see the only place for it is to move it higher above top cabinets. I also plan to add a couple of more ducts and probably one return duct. Again the only place I see for those additional ducts is in the walls above top cabinets. I cannot put them into ceiling because of ceiling joists. Any advise would be appreciated.
Don't go adding ducts without understanding the impaceon the rest of your system. A return duct in the kitchen sounds like a great way to get kitchen odors spread throughout the house. In some jurisdictions it is against the building code.
Putting toe space grills in houses with A/C and a basement or crawlspace can be a mistake. Normally, the duct is attached to the floor under the cabinet under the cabinet. This pressurizes the space under the cabinet with cold air. The subfloor under the cabinet assumes supply air temperature. If there is any humidity in the crawlspace or basement, moisture will condense on the underside of the subfloor. Conditions are then ripe for mold growth or wood rot. Even if you duct the air all the way to the grille, there can still be problems. The floor in front of the grille will also approach the supply air temperatures. About 10 percent of my business involves fixing problems with damp crawlspaces. The biggest problems are with houses with toespace grilles Avoid toe space grilles unless you are in a very dry climate.
Your plan is workable, especially since you are adding other supply ducts... you may want to eliminate the return duct though as that will take cooking odors all through the house.. you want the kitchen exhaust to take those outside as a rule. and you want the new supply air to move in a way that it does not interfere with the kitchen or stove top exhaust ..that means no supply air blowing on or around the stove top.
The supply air registers above the cabinets should ideally be in a facia flush with the front of the cabinets and be rated for wall placement, as contrasted to say ceiling registers that are configured differently.
The air should not just be dumped in a space atop the cabinets.
However adding more ducts could unbalance the system and deprive other parts of the house of air, so that the kitchen would run too cold in the summer and too hot in the winter.
To cure that put manual balancing dampers in the kitchen ducts so you can 'balance' the system later. If you rely on the supply air grill dampers you could get whistling. or you can do it as planned and see how it operates ..then add balancing dampers as required later.
There are thermostatically controlled dampers you can buy but thats a lot of complexity for a slight gain in your situation.
First, if I do it, it's ducted all the way to the grill.
Second, I live in an area where humidity isn't an issue.
Your thinking, and sharing your knowledge, that's good. That's the nice thing about the NG, it's made up of people from all different areas of knowledge.
Thank you for our response. I really understand now that putting a return register in the kitchen is not a good idea. I however wonder how to install forced air registers flush with cabinets facia. Registers are more then 4" height, facia must be really huge. Are there online resources preferably with pictures where I can see how registers are placed in kitchen?
if you have only 2" or so above the cabinets you might have to use 'slot diffusers'. take a sketch to your local sheet metal shop and see what they say.. it shouldnt be a problem... or they will have a source. Or call your local HVAC wholesaler and tell them you are a home owner looking for wall slot diffusers...however long but narrow...whatever space you have.
OR In your case I might build a sheet metal box behind the facia, flange it to the facia on the inside and cut 1/4"lots in the facia with a router. or dado blade in a skill saw.
We lived in the desert where COOLING was much more important than heating. Our kitchen ducts were placed above the cabinets..Picture cool air 'falling'. We were on a concrete slab so actually all the ductwork was "above" the living space. It sounds like you could add a run from the existing duct, up and along the tops of the cabinets and box it in with a bulkhead from cabinet tops to ceiling. I like to do that anyway when I build..finishes it off neater than just having the upper cabinets hanging on the wall and a dusty, clutter collecting "shelf"/tops above.
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