Stove Installation - Support Box & Attic Insulation Shield

[timfromohio]

I'm starting to figure out the components required to install my stove and have what is probably a pretty stupid question - if one uses a support box is an attic insulation shield also required? The stove will vent straight up through an attic space. The various manufacturers descriptions are a bit confusing - it seems some of the support boxes do provide for shielding from insulation - should an additional insulation shield be used for the portion of the chimney pipe between the top of the support box and the bottom of the interior roof surface?

Thanks for any input!

 

[JPapiPE]

What is the distance from the ceiling to the roof?

 

[timfromohio]

Very slight pitch to roof - I haven't crawled through the attic to meausure exactly yet - the distance is on the order of 4 feet (top of ceiling to bottom of roof as measured from inside attic). You need to be a midget ninja to work up there ...

 

[Hanko]

If you have insulation in your attic, you should use a shield

 

[snydley]

I'm starting to figure out the components required to install my stove and have what is probably a pretty stupid question - if one uses a support box is an attic insulation shield also required? The stove will vent straight up through an attic space. The various manufacturers descriptions are a bit confusing - it seems some of the support boxes do provide for shielding from insulation - should an additional insulation shield be used for the portion of the chimney pipe between the top of the support box and the bottom of the interior roof surface?

Thanks for any input!

The support boxes come in different lengths. My stove was installed in the N.W. corner of my ranch home, and the space between the attic floor and ceiling was less than 2 feet, so we got a 3' square box,(I believe), and went with the "roof supported" installation. If your "attic space" is less than the length of your support box, you can run the support box right up through the roof, split the metal at the corners, fold it over onto the roof and secure it there. Your support box also acts as the attic shield in this case.

 

[JPapiPE]

If the distance is less than 4' you might opt for a simpson 48" square cathederal ceiling support box. You hang this box 2" below the finished ceiling and run the box through the roof. This box gives you complete protection all the way up through the roof and you will not need an attic insulation shield. A box for 6" pipe measures 12"X12" and is probably cheaper than both a shorter ceiling support box and attic insulation shield combined. It is also called a cathederal ceiling support box, but can be used for flat ceiling installation. You run this up past the top of the roof and cut it about an inch longer than the roof surface ( contour to the roof) cut the corners and fold the flaps down onto the roof deck and secure. Lower additional framing is also added for strength and additional nailing. R.O. for this 6" box is 12-1/4"X 12-!/4". If you use this method the ventilated roof flashing is recommended. This is how I did my install. And do believe it is a superior system as no combustibles can get near your chimney in the attic.

I think the Simpson order # is 9438C

 

[begreen]

There are different types of ceiling support boxes. Some are shallow and open on the attic side. Others, like a cathedral ceiling support box are tall with a box-like enclosure above the support collar. In some cases the cathedral support box can be used in a non-cathedral roof setting. For example, where the flue goes up in the shallow knee-wall space of an attic. In this case the hole in the roof is cut to fit the support box which is trimmed long so that it protrudes through the roof, matching the roof pitch. The extension that protrudes through the roof is bent over as a flange and nailed to the roof.

Download the Simpson duravent installation manual for some good illustrations of the installation options.

 

[timfromohio]

Huge thanks to everybody that replied. This is such a great forum! I'm looking at the Duravent page now. I think that that the cathederal ceiling support box running through the attic is the way to go.

Thanks again.

 

[begreen]

If the flue run through the attic is greater than say 3 ft. I would use the shallow support box and an attic insulation shield.

 

[Hanko]

If the flue run through the attic is greater than say 3 ft. I would use the shallow support box and an attic insulation shield.

me feels that way too

 

[timfromohio]

OK, guys - a couple more questions:

1 - Brand preference and why?

2 - double-wall or triple-wall chimney pipe?

Thanks for opinions.

 

[JPapiPE]

I like Dura-Vent's products...as I like the idea of a non-settling blanket rather than a loose fill with the Selkirk...But supposedly Selkirk has fixed the settling problem. I did go with the Dura-Tech line of Simpson pipe because it seems to be more available...All are listed and fire certified...So maybe it's a personal choice

 

[begreen]

Any of the major brands are good - Simpson, Selkirk, or ICC. Double-wall class A is fine.

 

[bartlett920]

The insulation shield is for people with blown in insulation that is piled up high. But the kit comes with it why not use it? most bat insulation is not more than 6 inches thick and most ceiling joist are 2x6's if the standard size box installed properly pulls you 8 inches away from the bat insulatilon so you are within clearances for standard class a pipe because it has a 2" clearance to combustibles. On the other hand if you had blown in insulation and an attic fan there is a possibility that the fan could blow the insulation up against the pipe causing combustion so an attic sheild would be a smart idea. chime in if I am completely wrong veterans. my 2 cents

 

[begreen]

The insulation shield is always a good idea. A lot of times batt insulation has paper on it which needs to be kept away from the pipe. In a well insulated attic there will be a first layer of insulation between the ceiling joints and then another layer at right angles to the joists for a total of 12 to 16" of insulation.

 

[KWillets]

Comparing prices for Simpson, the short ceiling support box + insulation shield can be cheaper than a 36" cathedral ceiling box, which runs over $100. The deeper boxes are also a pain to nail in for a ceiling-supported installation -- I would recommend pre-drilling the nail/screw holes, or pre-framing on the ground before putting it in the ceiling.

 

[fisherman]

Can anyone help me

I have a ranch home and I am getting ready to install the new chimney ( actually replacing an old non compliant double wall only listed in Canada) and the duratech paperwork stated that I should use a fire radiation shield and the attic insulation sheield.

The problem is when I install the fire radiation shield it comes withing 1 inch of the slope roof in the attic and leave no room for the attic insulation shield. DO I STILL NEED TO do something else, even though the fire radiation sheild covers the entire location from the 1st floor ceiling to the bottom roof rafter?


Thanks