insulating 3 season porch

[toughguy]

I'm building a 3 season porch this spring and I am debating between putting in fiberglass insulation myself or having someone spray it. The porch will have baseboard heat that won't be on all the time. I'd like to use the room in the winter on weekends / holidays. It's going to be 14x14 with quality windows to help keep the heat in. I will be insulating the floor, walls and ceiling. Is there going to be a big advantage in going with spray foam? How much would spraying it cost?

[Pinusbanksiana]

Many advantages except price. If price is not an issue, spray foam all the way. It will be the way of the future for sure.

[Surface Tension]

Instead of insulating the floor and venting the crawl space consider going with a conditioned crawl space. Google "Conditioned Crawl Space"

If you won't go that route then check out "Clean Crawl Space"

[toughguy]

I have a walk out basement. The porch will be 9-10' in the air so I don't think a conditioned crawlspace will work. Sorry I didn't mention that in the original email. I plan to add plywood to the bottom of the joists after I add the insulation.

[Pinusbanksiana]

Putting the vapor barrier in properly in that situation is tricky, it has to be below the floor and above the insulation. The joists complicate things. I would really suggest spray foam for the floor.

[Timber]

I live in northern MN, and did the same thing you're talking about doing. I have 3-season room that's 12 x 12 and sits 8 ft. off the ground. The ceiling and walls are insulated, thermopane windows, but no insulation under the floor. I decided last year to insulate the floor and heat the room for use during the winter. I used 6 inch fiberglass insulation. Big mistake. Room was cold. I am going to re-do the floor insulation this summer, and will use foam insulation. I am going to put 3 layers of 2 inch foam, using canned spray foam to seal all the joints and cracks. This method is cheaper than having someone foam it. With foam you don't have to worry about a vapor barrier. With this I should get an R-value of over 30, compared to the 15 to 19 with the fiberglass. Less air infiltration also.

[toughguy]

Good info. Sounds like I will be using foam. Thanks,

[cavalierowner]

Something you may want to consider to get the maximum amount of insulation in that floor (in addition to spray foaming) is to add 1" to 1-1/2" of extruded polystyrene rigid insulation between the subfloor and the underlayment. That will give you a continuous layer of insulation with no thermal shorts at the joists for not a lot of extra money. In my opinion you can't have too much insulation in floor and ceiling systems.

[K_Josh87]

i would for sure foam the floor, and may as well do the rest... another more long term solution would be a soffit material underneath the floor joists... We built an addition like this for a guy last summer, turned out very nicely

we used a 6x12 laminated treated beam for the side set atop 6x6 posts to support main bearing points of the walls/roof... and then a 2x12 double header underneath the joists to support them with a 2' cant... worked very nice... very beefy when we where done...

[K_Josh87]

here is another shot...

[toughguy]

Good idea. Thanks for posting the pics

[Tom7227]

Whatever you do be sure to get good solid footings. Screwing that up will cost you a ton of dough in the long run. Cost a friend an incredible amount of money.

The other thing to think about is what happens under the room. In the posted pictures the three windows in the lower level are now shaded completely and so whatever room is on the inside is going to be much darker. It also impairs the view from those windows. No offense to the person who posted the pics meant.

I do like the fact that there is a slab under the addition. The only other thing that would concern me is the possibility that the area would become a dumping ground for bikes, lawn gear etc.

A bit off the subject but could someone give an idea of what it would cost to put full walls on the lower side? It always seems to me that maybe for not that much more money you could have an awful lot more room added to the house and maybe end up with a nice shop area. Not my intention to steal the thread.

[K_Josh87]

This customer already had a deck in the spot where this was built, so the view and what not really did not change for the lower level...

As to cost for the lower wall... your big expense would be the frost footings and slab, otherwise, framing would be pretty minimal in comparison to drilling holes and putting in pads for the posts, and building a frame for the upper level...

No offense taken! Its not my house, I just build what to customer wants! ;-)

[K_Josh87]

and YES FOOTINGS ARE VERY VERY VERY important... As stated, there was a deck previously built in this spot... it was very scary how that was sitting... and it caused this guy nothing but trouble, and part of the reason he did the addition was because he needed to redo the deck anyways...

[toughguy]

I'm going to go with 3 24" footings at 5' deep. I learned the footing lesson on my last house lol. I have 9' ceilings in the walkout so the view shouldn't be ruined as bad as it is in the pic.

[Tom7227]

I'm going to go with 3 24" footings at 5' deep. I learned the footing lesson on my last house lol.

What makes you think that 3 is enough? I have no idea how to figure that out so I am just wondering what goes into making that decision. I would think that the type of soil you end up with at the bottom of the hole would have a big impact on what is adequate.

[toughguy]

Code for that size structure is 3 at 48" I figured an extra foot is enough.

[Pinusbanksiana]

I did the 4 foot footings on my deck last summer. One of them ended up hitting the water table and was wet. That concerned me a little, still does.

[LightningBG]

I'm going to go with 3 24" footings at 5' deep. I learned the footing lesson on my last house lol.

[Biggerfish]

Correct,

# and size of footing's depends on the force going down to it and the type of soil.

Water in your hole is not a good thing unless it is 6' down.....

[toughguy]

I thought I would give an update on my project. I went ahead with spray foam on the floor and walls with blown insulation in the ceiling. I also added a 6 ft base board heater. So far everything is working great. The floor stays warm and the walls are tight. Another thing I noticed is when they were done applying the foam the entire structure really stiffened up. The foam essentially glues everything together. There are no squeaks or pops in the structure at all. I would heavily recommend spraying a porch if you build one. Thanks again for the info