Tapered batt insulation

[WolffG]

Is there a way to make tapered batt insulation?
This is often necessary at truss ends when I don't use an "energy" truss.
I've been using filled regions but that gets a bit messy

[sbrown]

I just use the insulation tool and change the size to a smaller width. You could create a detail component too.

[iru69]

Any other thoughts on this issue? This is extremely common scenario in residential construction.

I'm not even sure how you would use fill regions... go in between the bits of plywood and roofing and white those out?

[Scott Hopkins]

I just use the insulation tool and change the size to a smaller width.Same here...

[iru69]

Scott H., thanks for the response and example - I was wondering if that's what Scott B. was really suggesting... I guess that works.

I was ultimately able to achieve "good enough" with a combination of cut profiles, filled regions, detail lines, etc. - it's just a drag to think of doing it for more than one section.

[sbrown]

Yes, thats exactly what I do.

[ita]

"Squeezing" the insulation blanket is poor building practice and produces very poor energy efficiency - to the point where the cast of the insulation is questionable! this is what is being communicated in tapering the insulation barrier over structure.

Any reduction in the thickness of the blanket reduces the efficiency of the insulation layer significantly. The insulation blanket thickness has to be maintained - probably by counter battening - to prevent squeezing. Even reflective foil papers and cellular insulation rely on at least a 20mm air layer "attached" to their respective surfaces to be effective insulators.

It would seem that good detailing and construction practice alleviates the need for a detail method of "reducing "the thickness of the blanket - at the same time saving a client the cost of the additional energy for heating/cooling over the life of the structure.

[WolffG]

I agree that squeezing the insulation is not great practice, but there are times when it is unavoidable.

[sbrown]

Does the insulation baffle help when you "squeeze the insulation? Or is its sole job to provide a ventilation route for outside air.

[iru69]

Does the insulation baffle help when you "squeeze the insulation? Or is its sole job to provide a ventilation route for outside air.
As far as I understand, solely to provide a ventilation route.


It would seem that good detailing and construction practice alleviates the need for a detail method of "reducing "the thickness of the blanket - at the same time saving a client the cost of the additional energy for heating/cooling over the life of the structure.
Admirable sentiments, and certainly something worth consideration. However, not very realistic in my neck of the woods (I have to pick my battles with subcontractors - and that's not going to be one of them considering our mild climate). Also, I almost always indicate batt insulation, but blow-in insulation is also commonly used (which is what really necessitates a baffle).

[bclarch]

"Squeezing" the insulation blanket is poor building practice and produces very poor energy efficiency - to the point where the cast of the insulation is questionable! this is what is being communicated in tapering the insulation barrier over structure.
While it is true that compressing batt insulation reduces it's effectiveness you have to take an overall view. You are talking about the last foot or so at the perimeter. If you take a 100' x 80' structure where you compress the outer one foot you end up with the following. You have 360 SF of compressed insulation at the perimeter vs. 8,000 SF total. That is equal to 4.5%. In a larger building the percentage of perimeter to gross gets even smaller. On top of that, the insulating value is only reduced, not eliminated. So even if you lose 50% of your insulating value you are only losing 50% on 4.5%.

In addition, the long term benefits of adequate ventilation far outweigh the minor loss of efficiency of compressed insulation at the building perimeter. One of the biggest driving forces in heat transfer is delta T, the temperature difference between the conditioned and unconditioned space. Without adequate ventilation, the heat build up in an attic will have a greater effect on the air conditioning costs than the small decrease in insulating ability of the perimeter insulation. In the winter, adequate ventilation helps reduce the condensation that occurs when warm inside air filters into the attic. It also helps reduce ice dam formation. Attic condensation and ice damming can cause damage that is far costlier than the few pennies of energy lost due to compression of a few feet of insulation.

[Steve_Stafford]

While it is true that compressing batt insulation reduces it's effectiveness you have to take an overall view. You are talking about the last foot or so at the perimeter.A recent "box lunch" with an energy analysis firm claims that the majority of "loss" though the building envelope is at the edges or eaves of a bldg...

[neilcheshire]

Apologies for butting into this discussion. But waht is the insulation tool. I am still using 2000i and have never come across this tool before.

Regards

Neil

[J. Grouchy]

Apologies for butting into this discussion. But waht is the insulation tool. I am still using 2000i and have never come across this tool before.

Regards

Neil

this is a Revit thread...you're missing out! :D

[bclarch]

A recent "box lunch" with an energy analysis firm claims that the majority of "loss" though the building envelope is at the edges or eaves of a bldg...Does this energy analysis firm deal mostly with commercial projects? I have always understood that in residential work the leading source of energy loss is air leakage at doors and windows. This may have changed as builders have paid more attention to energy conserving construction practices. I was reacting mainly to Ita's point that compressed insulation is so useless as to be not worth installing. It all depends on how severely the insulation is compressed and for how great of an area of the insulation is compressed. In a residential project a 8" batt compressed to 6" or an 12" batt compressed to 8" for the last foot or so at the roof edge is not significantly compromised.

Also, "Majority of Loss" does not automatically mean "significant loss". Say a building has an insulating efficiency of 99%. Lets say that a majority ( we'll say 75%) of the energy loss occurs at the eaves. 75% of 1% is still only 0.75% of the overall project which is still 99% efficient. I'm obviously pulling exaggerated numbers out of the air to make a point but the point remains. You need to take an overall view when assessing how one imperfect detail affects the totality of the project.

[SCShell]

Hey there,

For what it's worth, here is my approach. Because I come from a "hand drafting" background, I never drew all of the batt insulation in any one location. (Partly from laziness, mostly from trying to keep the drawings clear.) I simply draw enough to shown where it goes and then I use arrows to indicate the extents and where it ends. The drawing notes describe the installation techniques and how wrap around objects or fill voids to insure full coverage.

I still do the same in Revit for the most part. I hate having the insulation cover the building elements at edges etc.

Hope this helps. (Remember, drawings are still an "art" and they are intended to explain the design, and your intent so that others understand what you are trying to show.)
Steve