# Insulate unheated basement? unique situation...



## godblsmnymkr (Feb 17, 2016)

i forgot to add: the living area is directly above this unheated basement with hardwood floors. it gets pretty cold in the house which may be a function of older windows but also the messed up insulation that is currently below the floor in the ceiling of the basement.


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## Windows on Wash (Aug 30, 2011)

Treat is like a crawlspace in this case. Use a combination of rigid foam and a proper vapor control layer (can be incorporated into the rigid foam) to insulate the joists and effectively move them into the conditioned space. 

I would cover the entirety of everything with something that the rats can't get behind like a thin plywood or similar building material. 

http://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces


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## GottaFixIt (Dec 3, 2010)

What is the basement floor made of?

Sounds like a dirt/rock floor, but you have water running across it?

The ideal "encapsulation" method (sealing off the outside and treating the entire inside as conditioned space) would still require water mitigation (you don't want standing water trapped under a vapor barrier) and won't fix the rat problem.

I think Windows on Wash is pointing you towards [Figure 7: Cavity Insulation with Vapor Barrier] on his buildingscience link. I believe that the best choice in your situation.

I don't know about rats, but we deal with mice a lot around here. They're almost impossible to keep out of anything that they want to get through including plywood. I think you may need to treat your rodent problem as a separate issue rather than trying to block them from the insulation, but a layer of tight wire welded fence may work to keep them out.


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## godblsmnymkr (Feb 17, 2016)

Nick DIY said:


> What is the basement floor made of?
> 
> Sounds like a dirt/rock floor, but you have water running across it?
> 
> ...


thanks for the helpful reply guys.
that hardware cloth is exactly what i was planning on using. try to seal off all the areas between the joists that i can, put hardware cloth on different ends of the joists to encapsulate certain areas of the insulation, and cover the whole basement ceiling with the hardware cloth overtop of the insulation. it will be a ton of work but hopefully worth it as it should keep the rats out of most areas, thus keeping the integrity of the Roxul insulation intact. 
the floor of the basement is bedrock with different levels. looks kinda like a mini mountain range. my dad was saying because the floor is exposed rock with not thermal resistance is why they put vapor barrier on cold side of insulation.

i'm also thinking of getting an energy audit done on my house and in turn asking them what they think is best for the basement. there are grants i can apply for through the power company that would basically pay for the job. 

so here's my basic strategy and tell me if you see any flaws with it.
rip out old soiled fiberglass batts. install Roxul 14 between the joists. cover with hardware cloth. seal with vapor barrier.
thanks for the advice guys its appreciated.


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## GottaFixIt (Dec 3, 2010)

godblsmnymkr said:


> so here's my basic strategy and tell me if you see any flaws with it.
> rip out old soiled fiberglass batts. install Roxul 14 between the joists. cover with hardware cloth. seal with vapor barrier.
> thanks for the advice guys its appreciated.



I think you should re-look at that link from Bud. The key to this system is encapsulating the joists/floor assembly in order to isolate from the cold side. The un-interrupted layer of foam board below the joists is the heart of the system. This means the joists themselves are warm, conditioned and protected from moisture.

In your case, that would probably mean rockwool in the bays, a layer of 2" foil faced polyiso(covers the vapor barrier), and probably some furring strips screwed through the foam into the joists to give you something to nail your cage to.

Make sure you don't have a vapor barrier somewhere in the floor assembly. You definitely don't want both. This can include vinyl flooring.


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## Windows on Wash (Aug 30, 2011)

Nick DIY said:


> I think you should re-look at that link from Bud. The key to this system is encapsulating the joists/floor assembly in order to isolate from the cold side. The un-interrupted layer of foam board below the joists is the heart of the system. This means the joists themselves are warm, conditioned and protected from moisture.
> 
> In your case, that would probably mean rockwool in the bays, a layer of 2" foil faced polyiso(covers the vapor barrier), and probably some furring strips screwed through the foam into the joists to give you something to nail your cage to.
> 
> Make sure you don't have a vapor barrier somewhere in the floor assembly. You definitely don't want both. This can include vinyl flooring.


Who the heck is Bud...? :biggrin2:


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## godblsmnymkr (Feb 17, 2016)

Nick DIY said:


> I think you should re-look at that link from Bud. The key to this system is encapsulating the joists/floor assembly in order to isolate from the cold side. The un-interrupted layer of foam board below the joists is the heart of the system. This means the joists themselves are warm, conditioned and protected from moisture.
> 
> In your case, that would probably mean rockwool in the bays, a layer of 2" foil faced polyiso(covers the vapor barrier), and probably some furring strips screwed through the foam into the joists to give you something to nail your cage to.
> 
> Make sure you don't have a vapor barrier somewhere in the floor assembly. You definitely don't want both. This can include vinyl flooring.


ok i re read it and understand the link. I'm not sure if putting polyiso on the cold side of the joists to protect them is worth it? 
1) there are pipes and heating ducts everywhere. it would be a nightmare cutting to fit everything around all the obstacles. 
2)i've noticed no mold or rot on the joists. i havent taken down the all the insulation yet so there might be some but so far havent seen anything. keep in mind this house is decades old. 
3) would probably make more sense to just spray foam the ceiling instead of some elaborate mix of different types of insulation, vapor barriers and hardware cloth. it would probably only cost a little more but the time and hassle it would save might be huge.
would spray foam be a viable solution for the ceiling to keep the upstairs warm and protect the ceiling from moisture?

i got quoted at $6000 to spray foam the ceiling, but that was for R28. if i halfed that it might be more economical. 
thanks for the help guys. I'm in over my head and i appreciate the help!


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## Windows on Wash (Aug 30, 2011)

If there is a bunch of mechanical and water lines, you can't insulate the floor as referenced for reasons other than difficulty. If you insulate the floor as the link I referenced does, you will create other issues like pipes freezing. 

You only have two options really and they are to insulated and condition the basement or insulate the floor. 

Well...option 3 is to leave it as is, but you still have the rodent issue. 

Maybe some pictures will help folks visualize what you have going on.


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## godblsmnymkr (Feb 17, 2016)

sure
heres a pic of the way the insulation is now with the vapor barrier ripped down
this is a more heavily congested area of the ceiling










heres a pic of a spot where i started to put the ROXUL in to replace the old insulation.
thats a pipe in the backround where water from the outside comes in from.










this is a pick of what the "floor" in the basement looks like. mountainous terrain with water coming in










another pick of a more typical area of the ceiling










now to be clear, I havent found any rot or mold on the ceiling. this house is decades old. does that mean no rot will occur or just a matter of time the way the insulation is done currently. i just have a hard time believing that after 30 years there is no rot, that rot could happen and therefore i need to condition the area of the joists. 
the coldest it gets is approx 21 Fahrenheit. therefore the basement would be warmer then that. maybe its not cold enough for the joists to rot?
thanks for the advice guys


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## GottaFixIt (Dec 3, 2010)

Windows on Wash said:


> Who the heck is Bud...? :biggrin2:


So sorry, got confused between two threads. Besides, Windows on Washington is way too long anyway. Do you have a preferred abbreviation?


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## GottaFixIt (Dec 3, 2010)

godblsmnymkr said:


> this is a pick of what the "floor" in the basement looks like. mountainous terrain with water coming in


That is the coolest crawlspace I've ever seen  Everything really is in amazingly good condition considering the water in there. Maybe between the flora and fauna in there, it's created a self regulating eco-system and you don't need to do anything, lol 

A cold side vapor barrier can be viable, but not with insulation that allows air movement by convection, which unfortunately, includes rockwool and other "soft" insulations. Well, at least not without the uninterrupted convection break that the foam board provides in the building science article. 

You are in a very difficult situation and I think investing on a closed cell spray foam may be your only good solution.


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## lenaitch (Feb 10, 2014)

That's quite an ecosystem down there. I'm surprised at the green plant live thriving in the dark.

_"Do you have a preferred abbreviation?"

_I think *WoW* is appropriate.


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## Nik333 (Mar 1, 2015)

lenaitch said:


> _"Do you have a preferred abbreviation?"
> 
> _I think *WoW* is appropriate.



Win is pretty good, too :}


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## Windows on Wash (Aug 30, 2011)

Nick DIY said:


> So sorry, got confused between two threads. Besides, Windows on Washington is way too long anyway. Do you have a preferred abbreviation?


WoW works like said below. 



Nick DIY said:


> That is the coolest crawlspace I've ever seen  Everything really is in amazingly good condition considering the water in there. Maybe between the flora and fauna in there, it's created a self regulating eco-system and you don't need to do anything


I agree with you. Crazy that this system is working. 

With all the mechanical and other stuff in there, the only think I can see to do is to frame the bottom of the joists down (i.e. scab in some lumber to create a new lower elevation) and then more easily insulated that lower surface. Otherwise you have so much stuff hanging down and around that it would take forever to get it all button up and some stuff would be outside the thermal boundary.


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## Nik333 (Mar 1, 2015)

WoW might be hard for some men to say :laugh:


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## godblsmnymkr (Feb 17, 2016)

thanks for all the replies guys.
actually, those are fake plants down there left from the previous owners so thats where the confusion comes from lol.

finally got to talk to my dad more about the situation. he said just to rigid board insulate the foundation walls, ripout all the old bad insulation from the ceiling, spray it with deck treatment to protect it from the moisture and thats it.
makes a lot of sense to me and will be far easier then the plan that i had.
only problem is its going to be a serious PITA to try to cut the bottom of the rigid board to fit the always different elevations of the ground. 
I guess the plan there would be to cut the bottom of the board to match the ground the best i could, then spray great stuff to fill in the cracks between the floor and the board where the cut wasnt perfect...
or spray foam insulate all the walls instead.
what do you guys think of this? what R value should I use for the walls? it would condition the basement and i think its a pretty good plan.
thanks


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## godblsmnymkr (Feb 17, 2016)

after doing a little big of research, Dow Thermax seems best to use in my situation. big problem i see though is the fact that water comes into the house through the foundation in a ton of different spots where the foundation meets the rock floor. not really sure what the solution would be in those spots...
just dont put anything there?


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## Windows on Wash (Aug 30, 2011)

I don't like insulating that wall and conditioning that space to be honest. How are you going to handle the moisture in the air via the water coming through the wall?


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## godblsmnymkr (Feb 17, 2016)

spray the wood ceiling with water proofing deck treatment. the rigid foam is water resistant right?
i contacted a well reviewed insulation company to see what they thought would be the best solution.


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## GottaFixIt (Dec 3, 2010)

godblsmnymkr said:


> ...the rigid foam is water resistant right?


No. Well, yes and no.

The problem is that XPS and polyiso (Thermax or Tuff-r) can both absorb water due to the cellular structure(polyiso actually being the worse of the 2). If this happens, the water acts as a conductor and negates it's insulating property. The foam would probably last for decades (if not centuries) like that, it just won't actually insulate.

Yours is one of the few applications that probably warrants the expense of Closed Cell SPF Spray Foam. It's the only option that I know of that is truly hydrophobic (will not absorb water) to the point that it can actually create it's own drainage plane. Mind you, this won't fix your water or rodent problem, but as far as insulation, it's the only viable choice.


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## Gary in WA (Mar 11, 2009)

godblsmnymkr said:


> spray the wood ceiling with water proofing deck treatment. the rigid foam is water resistant right?
> i contacted a well reviewed insulation company to see what they thought would be the best solution.



Welcome to the forum! Lay some 6-15 mil. plastic, same stuff used in a crawl-space on the rock, joints/laps taped/caulked (acoustical) to the foundation footing, above the rock joint. Your water drainage cannot be impeded by new insulation... Replace the floor cavity insulation (though the fiberglass appears to be compressed for a better R-value per inch) *to void insulating the walls*, as said, it has lasted this long with furnace ducts to facilitate drying of the joists with air/heat movement. OR, wrap the ducts to bring to code as the moisture problem will be stopped with sheeting on the rock. Caulk/foam all exterior penetrations against bugs/air infiltration. IF there is plywood underlayment, that is your vapor barrier from moisture source above. Add foil-faced foamboard to the rim cavities after air sealing all wood rim/plate/joist/sheathing with caulking. Add a housewrap (Tyvek-very open) to the joist bottoms to stop air R-value degradation. 

I used that BSC link (exclusively here) for 4 years 'til WoW recently took it as his own and now he needs the credit for using it here.... ironic, lol. Others may feel free to use it, as apparently it's the only one out there. :biggrin2:

Gary


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## godblsmnymkr (Feb 17, 2016)

hey thanks for the very thorough reply. i only understood about 1/2 of what you said :surprise:




Gary in WA said:


> Welcome to the forum! Lay some 6-15 mil. plastic, same stuff used in a crawl-space on the rock, joints/laps taped/caulked (acoustical) to the foundation footing, above the rock joint. Your water drainage cannot be impeded by new insulation... Replace the floor cavity insulation (though the fiberglass appears to be compressed for a better R-value per inch) *to void insulating the walls*, as said, it has lasted this long with furnace ducts to facilitate drying of the joists with air/heat movement. OR, wrap the ducts to bring to code as the moisture problem will be stopped with sheeting on the rock. Caulk/foam all exterior penetrations against bugs/air infiltration. IF there is plywood underlayment, that is your vapor barrier from moisture source above. Add foil-faced foamboard to the rim cavities after air sealing all wood rim/plate/joist/sheathing with caulking. Add a housewrap (Tyvek-very open) to the joist bottoms to stop air R-value degradation.
> 
> I used that BSC link (exclusively here) for 4 years 'til WoW recently took it as his own and now he needs the credit for using it here.... ironic, lol. Others may feel free to use it, as apparently it's the only one out there. :biggrin2:
> 
> Gary


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## Windows on Wash (Aug 30, 2011)

Exclusive Links...? Is that Golf or Chain?


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## godblsmnymkr (Feb 17, 2016)

ok getting the basement foundation walls spray foamed tomorrow morning. got a good price from a recommended contractor. i have worries over the amount of moisture down there. read a blog online about only insulating foundation walls of basements that are bone dry because moisture can get between the spray foam and rot the wood of the band board if its a wet basement. 
also not sure how effective it will be as so much of parts of my walls are the rock floor that wont be getting sprayed.


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## Gary in WA (Mar 11, 2009)

If the SPF is too thick, it will stop all moisture from coming through. This, in turn will keep more moisture in the concrete wall. Without the interior drying, it can only dry to the outside, not a problem except you might have a wood sill plate which will wick the excess moisture and rot the sill- if no sill sealer between it and the concrete. I fail to understand why you would insulate the walls when your thermal barrier is at the floor line. The walls can drain the moisture to the rock drainage system you now have. You won't gain much if the crawlspace is now ventilated. Just closing the vents requires more to make a "conditioned crawl", which is what it sounds like you want; http://www.google.com/url?sa=t&rct=...cxhZUUbjb19gdOLGMmhxgpg&bvm=bv.59026428,d.cGU

I meant I (exclusively) used that link until you took it last year. Similar to a child caught doing wrong; either make light of the situation or direct attention elsewhere- anything but admit wrongdoing; any parent is familiar with that ploy.

Gary


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## Windows on Wash (Aug 30, 2011)

> I meant I (exclusively) used that link until you took it last year. Similar to a child caught doing wrong; either make light of the situation or direct attention elsewhere- anything but admit wrongdoing; any parent is familiar with that ploy.


So you wrote this information for BSC and/or you are the only person to have used that link before? 

Is that it or do you have the expectation that only you can link to someone else's information that is approximately 6 years old and is in wide circulation in the building science and retrofit community? 

The humor, in this case, is used to help demonstrate the ludicrousness of your actions/attitude...not mine.


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