Last (hopfully) insulation question - Woodworking Talk - Woodworkers Forum
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post #1 of 16 Old 12-09-2018, 01:54 PM Thread Starter
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Last (hopfully) insulation question

Hopefully this is my last question regarding insulation for my basement project. I touched on this this before but wanted to see about a specific answer or recommendation.



Im looking at putting insulation in the roof joists of the basement. But im uncertain as to which option would be best.
I already have the roll faced insulation. (it was a discount if you buy enough. And enough just happened to be the amount it would take for all the walls, and the roof. And i needed to save money.)
https://www.lowes.com/pd/Owens-Corni...t-L/1000373565


Picture of one section of the roof in the basement. As you can see, many areas have a lot of nails coming down. It was that way when i got this place.








The roof joists are about 7-1/4" deep. And the insulation is 3.5" thick.


As far as i see atm, i have three main options with what i have.



1. put the insulation in and staple the face to the bottom of the joists. (Just like doing it in a 2x4 stud wall.) And have a large pocket of air/open space above it.


2. Push it all the way to the top. Seems like a bad idea since that many nails would likely compress the insulation.


3. Push it up to the nails but not into it, so it doesnt compress. Leaving a small bit of air/open space above it.; and also leaving a little bit of room below it so it wouldnt need stapled into the joists.



(#2 and 3 would be held up with insulation supports)
https://www.lowes.com/pd/600-Pack-In...5-5-in/3010245



Im guessing #2 or 3 would be the better option. But im not sure how that pocket of air would, small or large, would impact the insulation value. Also not sure if i want to cover the joist with face or not.
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post #2 of 16 Old 12-09-2018, 03:13 PM
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Does this insulation not have a tack strip as an integral part? If so just put the insulation between the joists and tack up. The nails will not bother the insulation.


George
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post #3 of 16 Old 12-09-2018, 03:17 PM
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I don't think any of those are bad solutions. Leaving an air gap doesn't make the insulation more efficient as air gaps have pretty much no R value. The nails won't bother the insulation a bit.
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post #4 of 16 Old 12-09-2018, 03:22 PM
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Why bother? Exposed fiberglass insulation is a occupational breathing hazard = you would need to cover it all with something else.
Your upstairs floors will be colder, insulated from rising warm air downstairs.
I'd insulate the walls for certain. Vapor barrier and drywalled, seals and all.


What does your building code say that you should be doing?
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post #5 of 16 Old 12-09-2018, 03:24 PM
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install the insulation with the vapor barrier paper on the top side with wire supports
anywhere above the bottom of the joist, air gap actually has r-value


homedepot.com/Simpson-Strong-Tie-16-in-Insulation-Support

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post #6 of 16 Old 12-09-2018, 03:28 PM
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The only thing that will effect the R value is compressing the insulation


I missed you other post or I might have read it and not sunk in (old fart syndrome) why are you insulating the a basement ceiling? There is no heat gain or loss if the basement is conditioned, and if not conditioned it would take forever for payback, very little heat load

There is no app for experience
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post #7 of 16 Old 12-09-2018, 04:02 PM Thread Starter
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the main floor of the house will be (id like it to be) heated. The basement room, for the pets however, must be kept cool. They can die from the heat. So i figured it would be a good idea to have some insulation between the rooms since the top room would be warmer and the bottom basement room needs to be cooler.



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Originally Posted by GeorgeC View Post
Does this insulation not have a tack strip as an integral part? If so just put the insulation between the joists and tack up. The nails will not bother the insulation.
George
I dont believe so. I havnt opened it yet, but this link is what i have
https://www.lowes.com/pd/Owens-Corni...t-L/1000373565







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The only thing that will effect the R value is compressing the insulation
Yea, that is what i was worried it would do. Im not sure if the insulation would just go around the nails, or if there are enough of them to just cause it to compress instead. I have a large section (under where the kitchen is i think) where there are a lot of nails coming through. (pics in next post. having issues with them in this one.)
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post #8 of 16 Old 12-09-2018, 04:03 PM Thread Starter
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post #9 of 16 Old 12-09-2018, 04:24 PM
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I don't think you would benefit from insulating the floor to keep heat from upstairs from transferring to the basement. Heat after all rises.

If you have your furnace and ductwork in the basement leakage of heat from that would probably contribute more heat than anything.
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post #10 of 16 Old 12-09-2018, 04:32 PM Thread Starter
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Quote:
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I don't think you would benefit from insulating the floor to keep heat from upstairs from transferring to the basement. Heat after all rises.

If you have your furnace and ductwork in the basement leakage of heat from that would probably contribute more heat than anything.

True. And the furnace and duct work is in the basement and does run along this section of roof.
While the main focus is to keep the basement room cool for the pets, i wont deny that i myself hate the cold. So i was thinking form the other direction; the cold penetrating to the upper main floor.
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post #11 of 16 Old 12-09-2018, 04:42 PM
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Quote:
Originally Posted by wolfgang953 View Post
True. And the furnace and duct work is in the basement and does run along this section of roof.
While the main focus is to keep the basement room cool for the pets, i wont deny that i myself hate the cold. So i was thinking form the other direction; the cold penetrating to the upper main floor.
When I lived in a house with a basement there was no insulation under the floor. I don't remember the floors being especially cold and the basement stayed around 50-60 degrees in winter. I think in the summer the temperature of the basement ran in the mid 70's. Of course there was bound to be a certain amount of cold that transferred through the un-insulated floor so insulation would help in that.
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post #12 of 16 Old 12-09-2018, 04:42 PM
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Heat rises, cold sinks, as said above. Perhaps a variable feed of outdoor cold air would be a useful design?
I have a walk in cold room with three adjustable vents cast right into the concrete basement wall.
Maintaining 4C is easy and 2 walls are bare concrete, the ceiling isn't insulated.


Are you keeping poikilotherms as pets? What's their preferred ambient temperature?
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post #13 of 16 Old 12-09-2018, 05:00 PM Thread Starter
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Are you keeping poikilotherms as pets? What's their preferred ambient temperature?

Chinchillas. I need to keep the room 70f or less at all times. preferably 65 or less. Temps at 75f can be enough to kill some of them. Some have a little better tolerance, some a bit less. Being in the basement should help with keeping things cool in itself. But if it gets to warm in the summer down there, i need to be able to cool it effectively and quickly. So while they 'should' be ok for the most part, im not into taking chances with there lives. Which is why im building the four walls with insulation. Doing the roof with insulation as well seemed like a natural thing to do. Both with keeping down there cool, and keeping the heat in the first floor there.


The last week or so, the basement has been a fairly constant 55f down there with the windows closed. We are just starting the cold seasons in PA, usa. So well see if or how much it changes as it gets colder outside. (And warmer when summer gets here next year.)


Random fyi; the other side of the basement will be home to a bunch of mice. They, like me, dont care for the cold much.
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post #14 of 16 Old 12-09-2018, 06:27 PM
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Thank you for the explanations. I'd make up a screened window insert that you had some control over air flow.
Just to have some cool air in spring and fall.

I doubt that you will have any issues all winter.

Summers at your place could be another story for heat and humidity.


I did that to vent my clothes dryer out doors in the summers.

Just Coroplast and plexiglas and some keys to hold it in place.
My basement seems pretty chilly in the summer time,

maybe the lower 4' actually in the ground with daylight windows.



I'm at 53N in a mountain valley in the Rockies. Nothing more than maybe 8500' around my house.
We feeeze and fry. My outdoor thermometer is in the shade = I've seen from 25 below to +115F.
Afternoon/west shade from a total wall of grape vines 2' out from the house.
Your pets would enjoy the grape leaves, they taste like the grapes!
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post #15 of 16 Old 12-09-2018, 06:59 PM Thread Starter
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Afternoon/west shade from a total wall of grape vines 2' out from the house.
Your pets would enjoy the grape leaves, they taste like the grapes!
Im not sure about the leaves, tho im guessing not. I think the vines themselves, when prepared properly are great chew items for the chins. Grapes themselves are very very bad for them however.






Quote:
Originally Posted by Brian T View Post
Thank you for the explanations. I'd make up a screened window insert that you had some control over air flow. Just to have some cool air in spring and fall.
The basement itself has three small windows in the cinder block through out. The previous owners filled in the fourth one when they built a enclosed porch (basically) over it.
The room in a room that i will be making is right in front of one of those windows. So i was going to add another small window at the same spot in the new room. So i can open both and have a kind of direct fresh air. - I was also going to add a normal window in other sections of the new room. Even tho they would only open to the air in the rest of the basement; if they are open along with the ones in the cinder block to the out side.. its the best i can really do for right now for fresh air flow.
(If thats unclear, i intend to make a final video laying out everything i plan on doing to give a full visual to it. You'll be able to see it then. I just want to figure out the last few things i already know of; like this roof insulation first.)
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post #16 of 16 Old 12-10-2018, 01:29 PM Thread Starter
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getting back on track with the insulation questions..


Quote:
Originally Posted by wolfgang953 View Post
Hopefully this is my last question regarding insulation for my basement project. I touched on this this before but wanted to see about a specific answer or recommendation.



Im looking at putting insulation in the roof joists of the basement. But im uncertain as to which option would be best.
I already have the roll faced insulation. (it was a discount if you buy enough. And enough just happened to be the amount it would take for all the walls, and the roof. And i needed to save money.)
https://www.lowes.com/pd/Owens-Corni...t-L/1000373565


Picture of one section of the roof in the basement. As you can see, many areas have a lot of nails coming down. It was that way when i got this place.








The roof joists are about 7-1/4" deep. And the insulation is 3.5" thick.


As far as i see atm, i have three main options with what i have.



1. put the insulation in and staple the face to the bottom of the joists. (Just like doing it in a 2x4 stud wall.) And have a large pocket of air/open space above it.


2. Push it all the way to the top. Seems like a bad idea since that many nails would likely compress the insulation.


3. Push it up to the nails but not into it, so it doesnt compress. Leaving a small bit of air/open space above it.; and also leaving a little bit of room below it so it wouldnt need stapled into the joists.



(#2 and 3 would be held up with insulation supports)
https://www.lowes.com/pd/600-Pack-In...5-5-in/3010245



Im guessing #2 or 3 would be the better option. But im not sure how that pocket of air would, small or large, would impact the insulation value. Also not sure if i want to cover the joist with face or not.



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