Re: Small A/C Unit on Back Porch
There are many products today that are designed for just such an application. Depending on the elevation of the porch, you may be able to feed the space from overhead or underneath. You did not indicate what if any attic space is overhead or crawlspace below. Be very, very careful about a zoning application to this space as most systems require no less than 25% of the total airflow within the system to be dedicated to an independent zone. If you ran one (1) 6" lead with a zoning damper to this area, and this was the only area that was calling for air, then the system would encounter problems.
Could you run a 6" lead from the existing system without adverse effect on the system? Probably. Would it provide you adequate heating and cooling to the space? Maybe.
I, myself would much rather resolve the problem intentionally, instead of accidentally.
It is (imho) a mis-application to use a "portable" air conditioning unit for your porch. Portable units are designed for temporary use, and I am concerned when I see this recommended as a permanent solution. It is not.
There are ductless systems that would enable you to mount a small fan coil unit on the garage wall and with a small opening route the lines, drain, etc. to a small outdoor unit. This would provide you with totally independent cooling (and heating) of this space.
You only mentioned a/c but, if it was me, I would be more interested in making this as much of a year-round space as possible. Now is the time to do so.
Have a professional HVAC contractor come in and perform a survey of the space and get his / their recommendations.
All the best, Irishmist
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