I have a screened porch with one side brick and three walls screens. The ceiling is 1/2 inch plywood. The window guys from window world are coming out in a week or two to install windows and remove all of the screens . I plan on adding r30 insulation on top of the plywood. I also plan on adding a supply and return duct, tapping off my existing hvac. I'd like to control it with a separate thermostat and dampers. I would add a 24vac transformer to power the thermostat and the dampers. Really I just need a switch but the thermostat would keep it from opening the dampers if I forget to turn the switch off. I'd really like some simple ideas or other suggestions.

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    Even if you get "good" windows, if you have windows all around, you will have a large area of low R-value - or high heating/cooling load. – Ecnerwal Jan 24 at 22:34
  • "simple ideas or other suggestions" for what? For the project as a whole? For windows? For insulation? For heat control? This is a broad question that could have many, many answers, and therefore, is not well suited to this site. Please be more specific in what you're asking about so that someone can give you specific answers. – FreeMan Jan 25 at 15:52
  • I was looking for ideas as a whole. But now that the project is finished, no further help is needed. The new windows turned out to insulated very well in cold temps. One 6x10 supply vent taped off of the existing air plenum also worked well as long as I keep the door to the main house open. – Timothy Ryan Apr 20 at 16:55

Your idea is full of holes as we like to say. As @Ecnerwal stated in his response, you have an area with a different heat loss and gain from the rest of the house. Just adding a supply and return duct will not provide a good result. It would be great if this idea would solve your problem but I doubt it will. If you live in a warm climate, this will not add enough cooling to be comfortable. If you live in a colder climate the reverse is true. To get the best results, you will need a dedicated unit to heat and cool this area unless you will be OK with what you get otherwise.

  • We have not had the high temperatures we normally get, but the few days we did get I was pleased with the cool temperature in the sunroom. I was not sure the existing hvac would be able to heat and cool the additional space, but now I know. – Timothy Ryan Apr 20 at 17:27

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