Question about insulation and replacing windows

[gatchel]

I know this is a garage forum but couldn't resist the wealth of knowledge here.

My question is about the house and changing out the windows. I will removing the old windows and installing new construction windows over the next few weeks. I am trying to decide whether or not it's worth packing out the windows 1" with wood so that the house can be wrapped with 1" foam board before we install vinyl siding this coming spring. I have searched for a R value comparison or something similar but haven't found what I am looking for. Adding 1" of foam should up the existing R value by 7 or so.

Is it worth doing for short or long them savings and adding a thermal break or is it a waste of time and money?

The reason we are doing new construction windows is because the existing brick mold is old and partially rotten and needs to be replaced on most of the windows. We figured with the new siding this spring it would be better to do a window with and integrated J channel for look and ease of siding later.

We are located in PA (Philly subs)with oil radiant baseboard heat.

What do you guys think.

Thanks for the help.

 

[Robert Haas]

First off if you are migrating the windows out past the "wet" line you need to properly flash the windows back to the dry line/barrier from the new windows nail on fin back to the existing windows seal point.

Also you are now increasing the wrap area at the head/jambs/sill area so consider the extra work on the interior. Sheet rock is cheap but the labor for the tape and texture can easily bust your budget and patients.

I would migrate the widows out board just to have the correct reveals after the siding is completed.

I am a general contractor that owns a glass and window company in California

 

[kmacht]

Adding insulation and housewrap to the outside of a house under siding will help quite a bit with keeping your house warm/cool. You are going to run into a problem trying to bump out a window though. Almost all of them are designed for a standard 2x4 or 2x6 wall stud and 1/2" sheeting. If you bump the window out you will end up with a gap inside next to your sheetrock. Most places that I have seen them do insulation compensate for the thickness by installing a wood trim piece next to the window and wrapping that with either vinyl or aluminum and then putting another j-channel next to that.

Keith

 

[gatchel]

First off if you are migrating the windows out past the "wet" line you need to properly flash the windows back to the dry line/barrier from the new windows nail on fin back to the existing windows seal point.

Also you are now increasing the wrap area at the head/jambs/sill area so consider the extra work on the interior. Sheet rock is cheap but the labor for the tape and texture can easily bust your budget and patients.

I would migrate the widows out board just to have the correct reveals after the siding is completed.

I am a general contractor that owns a glass and window company in California

Got it about the flashing.

I was planning on just using 1X? ripped down to extend the jambs and trim to that.

I will be moving the windows outward at this point because of the look from the outside.

Adding insulation and housewrap to the outside of a house under siding will help quite a bit with keeping your house warm/cool. You are going to run into a problem trying to bump out a window though. Almost all of them are designed for a standard 2x4 or 2x6 wall stud and 1/2" sheeting. If you bump the window out you will end up with a gap inside next to your sheetrock. Most places that I have seen them do insulation compensate for the thickness by installing a wood trim piece next to the window and wrapping that with either vinyl or aluminum and then putting another j-channel next to that.

Keith

The insulation was my main concern as far as costs go. I'd like to make it more comfortable and also save some money on fuel and electric while taking advantage of the 30% tax credits that are available.

Fortunately there is no sheetrock. Plaster walls dead end into the window frame (jamb) on the interior and there is trim to cover the joint. I will be making my own jamb extension by ripping down 1Xs to fill from the window frame to the interior trim.


Thanks for the feedback!

 

[70redbee]

Why not replace your windows,remove the old siding,add housewrap and then use the vinyl siding that is made with the foam already on it to gain the r-value. Insulate well around the windows before retrimming. No need to add wood around the outside or the inside,everything comes out as if you never had any changes,except better windows and a nicer exterior look.

 

[little jimmy]

Sounds like you are doing exactly what we did on our house last year. We used 1/2 inch plywood to bring the windows out and then when we put r board on it matched up to the plywood. The sideing lined up and was easy to do. To finish the inside I ripped extension jams and added to the window frame then trimmed them out. Yes it was a little messing around but it was the only way I could see to get it done when the construction was spread out so long. Our house is well over a hundred years old and my wife and I have been working to remoudel it one room at a time for six long years but we are almost done. Oh and yes RBoard and house wrap along with new windows and siding made our house feel better then I could have ever hoped for. Good luck.

 

[walrus]

What do you guys think.

Thanks for the help.

R10 is the magic number, its where any moisture in your wall won't ever hit dew point and turn to water.
www.buildingscience.com I'd want 1.5 inches of foam

 

[jj mack]

Like it was said before...you can fur out the window as much as you want as long as you flash them properly to the weather resistant barrier...ie housewrap. adding the insulation to the exterior side is a good thing. It moves the due point out away from the wall.

As far as the inside, check with the window supplier, they have jamb extensions to help solve the issues on the inside with aesthetics.

 

[tcianci]

Does your house have a hip roof or a gable roof? If you have a gable roof, adding an inch to the wall can push your J channel under the rakes out too far. It's usually a bad detail on a vinyl job anyway as far as looks and water penetration goes. Just look out for any of the details that will either be compormised or just look like *** (vinyl corner boards, and the J channel at the rakes like I mentioned if the house doesn't have overhangs on the rakes as well as a soffit) The style of rakes is usually a regional thing Up here in MA, most houses do not have overhangs on the rakes. Can I ask why if you're planning to side the building, you just dont have insulation blown in before the siding job?

 

[gatchel]

Does your house have a hip roof or a gable roof? If you have a gable roof, adding an inch to the wall can push your J channel under the rakes out too far. It's usually a bad detail on a vinyl job anyway as far as looks and water penetration goes. Just look out for any of the details that will either be compormised or just look like *** (vinyl corner boards, and the J channel at the rakes like I mentioned if the house doesn't have overhangs on the rakes as well as a soffit) The style of rakes is usually a regional thing Up here in MA, most houses do not have overhangs on the rakes. Can I ask why if you're planning to side the building, you just dont have insulation blown in before the siding job?

Gable roof. It will look like *** under the rakes for a few years. I will flash and caulk to handle the water runoff for now. I plan to re-roof in 5 years or so. When this happens I will build out the rakes and make everything right.

As far as blow in insulation, I didn't think I could with existing batt insulation in the stud cavity.