Help sizing man cave

SeanBeans

A friend is converting his 4 car garage into a man cave, and building a new 2 car garage on his property.

He wants a 3 head minisplit system installed..

The current structure is 1164 sq. Ft
Will have approxinately 128sq ft of windows.. he is planning to buy the cheaoest windows he can find but still double pane.

The roof will be spray foamed with R-30 and the walls R-13

The structure measures 48' +/- 2' x 24' +/- 2'.. the heigh if the ceiling will be approximately 16 feet tall.. they are doing away with the attic space and it will be one giant room

On top of this, he will have roughly 20-30 friends over at the most at any given time.

Is there an app to help size this?
I learned how to do manual J in trade school but it has been years.

I dont want to undersize it so when hes got 30 people over it doesnt cool..


Please help, TIA

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SeanBeans

ChrisJ

Ok I'm a little confused.

I realize, you didn't ask this and I'm sorry but I have to ask.

He's buying the cheapest windows possible, but using sprayfoam?

Personally I'd be going all fiberglass and buying good windows. Sprayfoam and cheap windows seems very counter productive and like a huge waste of money.

Rich_49

Windows are kinda funny . To really get a good window would cost 3 -4 xs as much as a basic window and then , even the best window is still a sh*&%y wall . Tell your friend to research using Roxul for his insulation and getting a basic , middle of the road window . What type foam was he thinking of using , open or closed ?

Another thing about Mini splits , especially in an area with high ceilings is that they don't work real well . The heated air rises and leaves those things on the floor cold , ya know , the people . Problem has arisen several times in very tight houses where folks have had to set room temp to 80* to be comfortable where they are .

Remember , hot air rises . Good news is that with 30 people there may be no load at all with 12,000 BTUs in the room

Gordy

According to the print notes this is an existing structure.

The architect is noting r-38 for the ceiling. The rafters are 2x8's. No go unless it's furred out considerably, which is also noted. So spray foam may be the answer, or at least a wash in cost as compared to furring the joists to accomidate enough fiberglass to get an r-38.

Curious as to the usage between parties? Is this going to be a venue of some sort, or just a man cave. If it's going to sit cold between activities something to think about in your conditioning requirements.

Ceiling fans would help push the warm air down during heating.

ChrisJ

Does anyone have that insulation comparison chart?
It was similar to the one for steam piping, but for walls and attic.

I recall R4 to R8 being a huge difference from nothing, but as you went above that the effect got smaller and smaller. I'm not sure what minimum code requires in that area, but perhaps just filling the rafters would be enough?

@Rich Agree on windows, except that the cheaper they are, the shorter they last. I've heard of cheap ones being garbage in only a few years.

Insulation aside, I'd still do good windows over spray foam. Spray foam is nice for many reasons, moisture being one of them but fiberglass isn't bad either.


Totally off topic but, they're removing the attic floor and leaving those tiny collar ties that high up? Has an engineer approved this? Usually you see collar ties much lower down to keep the rafters from pushing the walls apart, which usually is the job of the joists. @Gordy Any thoughts? That, at least on the drawing doesn't look strong at all.

Bob Bona_4

First third of the rafters is what I've been told for collar ties. Off topic

ChrisJ

Bob Bona said:

First third of the rafters is what I've been told for collar ties. Off topic

Bottom third, correct?

Gordy

Well, I'm thinking maybe wrongly so that "attic floor to be removed" is solely the flooring, and not the joists. However The joists have a note 3 1/2 X 11 7/8 PSL. That's a micro lam beam. So with out more details I would assume beams are replacing the attic floor at wider centers to open it up. The collar ties must remain in the upper third. Especially with the added load of the dormers. On one side no less.

Edit: That transition from demo of attic floor, and adding beams must be done together as you go, or some bad things could happen. Especially with the collar ties much higher than the top 1/3.

Gordy

Another thing I missed on the initial post is the intent of sizing for cooling verses heating.