# Insulating Attic Space



## Etrace0921 (Jan 15, 2012)

Hello all,

I am looking for some advice pertaining to insulating my attic space, in particular, the attic floor.

I live in a small 1 story Victorian home in central IL that has a very usable and spacious attic (with full staircase) which is unfinished and mainly used for storage. I have read that the attic is a good place to start as far as energy savings and comfort go. 

The floor of the attic is made of 6" tongue and groove boards, and the subfloor (main level ceiling) consists of 2"x6" joist 16" OC. The previous homeowners did a terrible and incomplete job insulating and the matted up, scattered cellulose present is hardly effective, as evidenced by my heating bills and the frequent ice dams during the winter months. 

I would like to insulate this floor, but I have questions pertaining to what vapor barrier is necessary, where it should go, and what type of insulation I should use (spray, cellulose, batt) I have plaster/lathe ceilings below, so removing those to do this is a no-no and this job must be approached from the attic, so the existing floor must come off. I plan on repurposing the existing floor, and replacing it with 3/4" plywood.

Any help or advice would be appreciated. Thanks!

Elias


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## Gary in WA (Mar 11, 2009)

Welcome to the forums!

1. What will be the final purpose of the space?

Check your joists to find if they can support the intended live loads- measure the distance between walls below: sleeping rooms are 30#, other are 40#: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_5_sec002_par017.htm

We'll go from there...

Gary


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## Etrace0921 (Jan 15, 2012)

Currently the attic is not used as living space, and we haven't yet decided whether or not we'd like to put the time and $ in to finish it out. I will, however, take the time and opportunity to reinforce the joists while the floor is off prior to insulating just in case we (and we most likely eventually will) decide to finish the space out. I have consulted an engineer and he agrees that sistering another joist to the existing ones will be sufficient to support current live load criteria for the existing spans. So once that reinforcing is done I will be insulating the floor. So to answer your question, we eventually will finish the space. Thanks!


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## AndyGump (Sep 26, 2010)

> we eventually will finish the space.


As what?

Bedroom?
Recreation room?
Storage only?

Andy.


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## Etrace0921 (Jan 15, 2012)

Sorry, as a master bedroom suite (bedroom, bathroom with shower only, closet, storage).


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## jklingel (Dec 21, 2008)

Before you decide to condition the attic, be sure to check into what will be required to insulate/air seal the roof of that space. If the area will be conditioned space, then there is no need to insulate the floor. Maybe just bag the idea of floor insulation and work on the roof. Vapor barrier??? WHY?


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## Gary in WA (Mar 11, 2009)

Good to know that you have professional help where you need it! The sistering is second, after the permit. Will you be doing the wiring, plumbing or HVAC yourself?

Gary


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## AndyGump (Sep 26, 2010)

You have answered the first question that should be asking yourself, You know what you want the space to be.

The second question you need to ask yourself is "do I want the added peace of mind of getting this project approved by the local authorities 'Planning & Building Departments'? ie. getting permits.

If you decide that that is a yes then you will need the project designed by someone that kows what the Building Department is going to expect to see on a set of plans. Engineering if not "conventional light frame construction".

Then when you have those and the approval ask yourself "Holy [email protected]! Do I really want to do all this or should I hire someone to do part or all of it.

Andy.


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## oh'mike (Sep 18, 2009)

As a side note----That is an old house and may still have knob and tube electrical wiring---

If you have that----update the wiring before you insulate----


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## Windows on Wash (Aug 30, 2011)

+1,000

Good eye Mike.


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## Etrace0921 (Jan 15, 2012)

Wiring is all updated. I understand the implication and nuances of finishing the attic. I have professional help available to me when and if I decide to do that. This post is not to discuss those, however. I merely would like some advice on the different insulating options available. Also, I'd like to know the specifics on what vapor barrier to use (if one is even necessary), where to put it, etc. as well as specifics for the insulation itself. Thanks!


-E


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## jklingel (Dec 21, 2008)

Etrace0921 said:


> Also, I'd like to know the specifics on what vapor barrier to use (if one is even necessary), where to put it, etc. as well as specifics for the insulation itself. Thanks!
> -E


 Structurally, the vb is probably NOT necessary, and likely not even helpful, and maybe a tad to a lot harmful (esp w/ air conditioning). Your code may mandate one, though. There is a product called MemBrain, made by CertainTeed, that is apparently a very good product. I will possibly use it in my house, where it is generally very cold and dry and a vb is less problematic. Don't use a vb just because "everybody does"; everybody USED to.


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## AndyGump (Sep 26, 2010)

Etrace0921 said:


> Wiring is all updated. I understand the implication and nuances of finishing the attic. I have professional help available to me when and if I decide to do that. This post is not to discuss those, however. I merely would like some advice on the different insulating options available. Also, I'd like to know the specifics on what vapor barrier to use (if one is even necessary), where to put it, etc. as well as specifics for the insulation itself. Thanks!
> 
> 
> -E


Great! You have "professional help" Good thing that you are asking specific questions about insulating the floor of an attic room that you intend to make into living space in the future. 
No real need to be bothered with little details like the structural necessity of what you intend to do, just give you only the pertinent facts about insulating the floor.

Great.

Andy.


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## Etrace0921 (Jan 15, 2012)

Well what I'm looking for is just some opinions on what products you might use to insulate the floor. I'm considering foam, as that would provide a tight seal but it's also expensive, and if I could get by with using batts for now (if I decide to finish the space I will probably spray the roof) I would prefer to do so. Also, would you consider putting cellulose in the cavities? Is there an advantage to using cellulose over batts? And what, if any, vapor barrier would need to be used in those instances? Don't mean to be writing off any of your advice, as it is important, but I do have professional help when it comes to preparing the structure so I'm not too worried about learning about that. There's a very real possibility that we won't finish the space, so I'm looking for the best solution to insulate the floor as that is really all I'm concerned with now and in the immediate future. Thanks!


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