Characteristics of a Screen Porch / 3- Season / Sunroom

For those of you who love the outdoors and want to sit back, relax and enjoy nature without having the bugs eat you alive or get wet from rain, a screen porch / 3- season room / sun room are usually at the top of your list when we start designing a space. But what is the difference between the three options? Conditioning and finishes is the easy answer.



When I refer to conditioned or unconditioned space, I mean heated and insulated or simply lumber against the elements. In the North East, it’s important to distinguish between the two for two reasons: 1. Code and 2. Cost.

SCREEN PORCH: This is literally just a framed room on footings (that do go down into the ground 4’-0” and framing / roofing / siding and finishes are fairly minimal. This can be used truly just when the temperature cooperates, typically just in the summer months in New England.

3-SEASON: We can move from a screen porch to a 3-seaon porch fairly easy with a few key components and not change the overall design. This would involve a combination or accumulation of adding windows, insulation at the floor joists, adding a heat source of fireplace or similar and locating it in a passive solar location on the lot. This space might be able to be used 3 seasons but not months or days that are sub-freezing with overcast.

SUNROOM: I would consider a Sunroom as fully conditioned, heated, insulated and using double-pane windows and doors. The only difference between this space and any other space in your home would be the fact that it has a significant number of windows. This is a room that is fully conditioned and usable year-round.


I’m currently designing a house located in Kittery Point, Maine and they truly want a 3- Season. I know that they will use it during the holidays and turn on the fireplace to get the added square footage but for the most part they will just use it during the summer when they are entertaining and have family living with them. There are large bi-fold glass doors connecting the two spaces and the exterior deck so that it feels open and light but in the winter it will feel safe and cozy when they are all closed up.


There is absolutely no right or wrong, I just always urge my clients to consider long-term and overall goal usage of the space. All home are custom so make it be and function the way that you want and need it to.


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