Insulating a bow window

[HomerJ]

I have a client who's insisting we somehow insulate the bottom of this window.

(Pella bow window with 5 casements. Unfinished wood interior with enduraclad white aluminum exterior. Width is approx. 110")

He believes it's silly to buy a new window to increase energy efficiency, and not insulate the bottom of it

There's nothing in the installation instructions about insulating the bottom. All the other instructions have been followed to the letter.

The bottom is plywood, and he suggested covering it with 1/2 insulation sheating. (the pink stuff) then covering the bottom with aluminum. I think that could interfere with the bottom frame expander and cause water to collect inside.

We built wooden knee braces to help support the window along with the cables. We were going to wrap those with aluminum, and finish insulating and wrapping the rest as stated in the installation instructions.

Would you insulate the bottom, and if so, how?

I can't post links to the window and install instructions yet, but they can be found at pella.com

[TulsaRemodeler]

I have a client who's insisting we somehow insulate the bottom of this window.

(Pella bow window with 5 casements. Unfinished wood interior with enduraclad white aluminum exterior. Width is approx. 110")

He believes it's silly to buy a new window to increase energy efficiency, and not insulate the bottom of it

There's nothing in the installation instructions about insulating the bottom. All the other instructions have been followed to the letter.

The bottom is plywood, and he suggested covering it with 1/2 insulation sheating. (the pink stuff) then covering the bottom with aluminum. I think that could interfere with the bottom frame expander and cause water to collect inside.

We built wooden knee braces to help support the window along with the cables. We were going to wrap those with aluminum, and finish insulating and wrapping the rest as stated in the installation instructions.

Would you insulate the bottom, and if so, how?

I can't post links to the window and install instructions yet, but they can be found at pella.com
Dont exactly understand the installation you have going on but covering the bottom with aluminum sounds dumb, that would be a heat/cold sink. Why not leave a gap that you can spray some Greatstuff in, they make a formula that is safe to use around window frames, dont use the regular formula as it can exert damaging force on some window frames.

[Mike(VA)]

I think he means the entire base of the bow that extends out from the house. Typically the underside is not insulated and his HO wants to insulate it and he has corbels underneath it.

One way to effectively insulate it would be to attach a 3" or so foam board to the underside, build a new bottom, add trim but keep it inside the existing trim to keep water out, caulk and paint. Corbels can be added for cosmetic purposes after that.

Is it a 30* bow? Bow windows don't typically need corbels for support but if this one does, you can put small squash blocks at point loads.

[HomerJ]

I think he means the entire base of the bow that extends out from the house. Typically the underside is not insulated and his HO wants to insulate it and he has corbels underneath it.

One way to effectively insulate it would be to attach a 3" or so foam board to the underside, build a new bottom, add trim but keep it inside the existing trim to keep water out, caulk and paint. Corbels can be added for cosmetic purposes after that.

Is it a 30* bow? Bow windows don't typically need corbels for support but if this one does, you can put small squash blocks at point loads.

You are correct about the entire base of the bow that extends out from the house not being insulated.

I think we're gonna build a frame to accomodate the insulation and step it back from the front edge so that water doesn't drip down inside.

The rest of the trim is aluminum, so we'll wrap the bottom as well.

Thanks for your input.