Insulating Attic - Topping Up - Install help! - DIY Chatroom

Nooch · 10-31-2009, 11:37 PM

Hi,

I live in Canada so have below zero temps. As such, I am looking to top up my existing R20 batt insulation to the recommended R50. The R20 has a thin layer of wood shavings on top of them. I am going to blow in an additional R30 of cellulose loose fill insulation. I know that I have to ensure the soffit vents are not blocked with insulation when I blow in the loose fill; however, I am not sure if I am doing this right.

Q1: Wherever there is a soffit, the original builder has nailed a piece of plywood which looks like it would be a baffle type idea. The home is 30 years old. I am looking at stapling additional cardbpard baffles on top of these to extend their distance up the roof rafters so as to avoid insulation getting blown in there. Does this make sense?

Q2: Also, do I need to staple a cardboard baffle at each rafter, even if no soffit there?

Please help!

Thanks!

oh'mike · 11-01-2009, 12:56 AM

You have done your homework! You get an A.

Extend your baffles and fill her up!--MIKE--

GBR in WA · 11-01-2009, 01:48 AM

"Q1: Wherever there is a soffit, the original builder has nailed a piece of plywood which looks like it would be a baffle type idea. The home is 30 years old." ------ If the soffit venting is not in every bay, you will have dead air spaces that are not vented and could help to cause ice dams. Especially if you have heated air from below escaping to the attic. But with every bay vented, the heat won't reach the roof deck in any area to cause them. I suggest using rigid foam boards at the exterior wall area to make up for the insulation bulk loss due to the rake of the roof there. You may have only 2-2" holes in every other bay, common for the way I used to frame roofs back then. If so, drill same holes in every bay. If closed soffit, this would be way under-sized. Use 1/100, not 1/150: http://www.airvent.com/homeowner/pro...it-specs.shtml

"Q2: Also, do I need to staple a cardboard baffle at each rafter, even if no soffit there?" ---- Not if there aren't holes there, as already answered. They would not have any air supply to rise to the continuous ridge venting with baffles.
Be safe, Gary

Nooch · 11-01-2009, 02:14 AM

Quote:

Originally Posted by GBR in WA

"Q1: Wherever there is a soffit, the original builder has nailed a piece of plywood which looks like it would be a baffle type idea. The home is 30 years old." ------ If the soffit venting is not in every bay, you will have dead air spaces that are not vented and could help to cause ice dams. Especially if you have heated air from below escaping to the attic. But with every bay vented, the heat won't reach the roof deck in any area to cause them. I suggest using rigid foam boards at the exterior wall area to make up for the insulation bulk loss due to the rake of the roof there. You may have only 2-2" holes in every other bay, common for the way I used to frame roofs back then. If so, drill same holes in every bay. If closed soffit, this would be way under-sized. Use 1/100, not 1/150: http://www.airvent.com/homeowner/pro...it-specs.shtml

"Q2: Also, do I need to staple a cardboard baffle at each rafter, even if no soffit there?" ---- Not if there aren't holes there, as already answered. They would not have any air supply to rise to the continuous ridge venting with baffles.
Be safe, Gary

Q1: Sorry, just to clarify these points...what do you means by "closed soffits." Additionally, what holes are you referring to that have to be drilled?

Q2: Not sure what you means by "continuous ridge venting." By holes, you mean whether there is a similar spacing between the roof deck overhang and joists?

Thank you!

Maintenance 6 · 11-01-2009, 08:17 AM

You don't want insulation touching the bottom of the roof surface regardless of whether or not there are vents in that rafter bay. Even without a vent there is some airflow under the roof surface that keeps it dry. Extend your baffles in all rafter bays.

ccarlisle · 11-01-2009, 08:46 AM

You may not have a continuos ridge vent where you are...that's an opening all along the peak (top part) of your roof, the highest part of it and it is a vent that allows the air to exit your attic. Where exactly are you?

Nooch · 11-01-2009, 10:11 AM

Thanks, I thought thst could be what you were saying. No, I don't have a continuous roof vent, I have several regular plastic vents throughout the attic. I live in Winnipeg, Manitoba, Canada. I've seen several homes with the continuous venting, so I understand.

So some say extend all baffles in all rafter bays. Can I use my cardboard cut outs for this or should I be using a Styrofoam baffles and trying to shove it down as far as possible down the roof line. I have a 12-12 pitch and the soffit/end of roof line is quite far down.

Thanks!

ccarlisle · 11-01-2009, 10:31 AM

Yes, you should extend the baffle system you use (whether it's those foam cutouts or something you make yourself, doesn't matter) as long as you keep the cellulose away fromt he underside of the roof...apart from allowing air circulation from the soffits holes up along the roof into your attic, the bafffles system just keeps the insulation dry.

Lots of Winnipeg clowns in town today

LOL!

Nooch · 11-01-2009, 10:42 AM

Thanks!

And to confirm, I have no pot lights, so nothing special to do on regular lights already installed in the ceiling via standard boxes? No heating venting outside the attic, only 2 bathroom vents which look like someone had wrapped in some sort of silver foil and taped using the silver ductwork tape. Do I need to do anything else then to prep?

Thanks again!

GBR in WA · 11-01-2009, 02:15 PM

"Wherever there is a soffit, the original builder has nailed a piece of plywood which looks like it would be a baffle type idea." ---- Do you have a closed soffit or an open one? 1. Can you see the rafter tails from the ground? 2. Are the covered by material installed to rafter bottoms, either level or on the slope?

If you are still uncertain, a picture would help of the soffit vents.
I understood it by "Wherever" you said- the vents are only in every other rafter bay. Is that correct?

You need to air seal the attic from the conditioned space of all air leaks penetrating the ceiling. Light boxes need to be caulked to the ceiling material, any wiring, around pipes (use special fire-rated material around B-vents from gas appliances), and insulate and wrap a vapor barrier around the bath fan ducting to prevent condensation from dripping and collecting. Also causing warm spots on the roof deck for ice dams, if close enough. I would suggest foil taping the elbow joints also, if present. They come apart quite easily while installing the insulation wrap and v.b.
Be safe, Gary

Nooch · 11-01-2009, 02:35 PM

Ok, just so we're on the same page, I'm attaching pics.

Soffit 1 and 2 are showing you what I have for soffits.

Then I took some pics of the attic (1-3). One gives you an idea of what I mean by the plywood baffles. I have 9 soffits in total around the house, so these are lead into these plywood type baffles. The second attic pic is just showing you my vent (btw, do I need to secure down any junction boxes that wries are running into or is this ok to leave)? Number 3 shows you what I was thinking of adding n top of the plywood baffles to extend them, but only at the plywood.

I noticed that the batt insulation actually tucks right into the other areas where there are no soffts, so any point to even putting baffles there?

Thanks very much!!!

ccarlisle · 11-01-2009, 09:18 PM

Know what? that's the first I've ever heard of using wood chips for insulation...I just thought one of the important properties of insulation was that the material was inert...fibreglass, cellulose, rock wool...all are inert, or treated chemically to resist attack.

Nooch · 11-01-2009, 10:21 PM

Funny, I thought it was odd too, but after speaking to various insulation people, apparently it's fairly common (maybe here)?

Any comments on my set up?

Thanks again!

ccarlisle · 11-02-2009, 08:15 AM

Just looked it up...wood chip have R1 insulation value per inch. This compares to R3 to R5 per inch for most products you buy to put there. Maybe you have an excess of wood chips in Mantioba? Just seems like a lot of effort unless you were hoping to get rid of it. Don't they also absorb moisture? Wood is naturally something like 10% water at least and when dried would tend to absorb it, no?

Nooch · 11-02-2009, 12:24 PM

Good to know.

Out of curiosity, can I blow insulation right over that bathroom fan vent (shown in my pic)? or do I need to create a baffle around it as you would do with recessed lighting?

Thanks!