attic insulation question

[Homerboy]

I have (very old) "blown in" insulation in my attic space.
However, I can tell that I am losing a lot of heat around the chimney stack and other areas of the roof as when I go outside after a snow/frost that area is melted away very quickly.

I have some left-over bat insulation sitting in my garage from some earlier remodeling projects. Can I just roll that out over the blown-in where the heat is being lost?

I know this isn't the "ideal fix" but I'd like to save a few pennies in heat loss and not "burn" money on buying new insulation at this point (not to muention due to the location(s) and access to the attic space, getting some bat insualtion in there would be WAY easier then dealing with blown)

Thoughts?

Thanks.

 

[nickbits]

Use fire rated insulation near a chimney

 

[hdfxst]

you can use whatever insulation you want.the chimney is not that hot that far from the furnace and if it does get hot the flue pipe broke apart and you have a much bigger problem

 

[3chordcharlie]

How much blown in insulation do you have?

In general, yes you can add insulation on top of what is there. I might have some concerns about insulating around the chimney - I assume it's not just the heat from your furnace melting things?

Blown insulation is the cheapest, easiest way to improve attic insulation, and as far as being easier, if you can access it, you can easily blow it.

When I did my attic there was a thin layer of existing insulation (4-5") to which I added about 10-12" on top. Here in the real world, my gas bill dropped 10%, or about $15/mo. I'm unsure how much my summer A/C bill decreased as I insulated before going through a summer in the house.

Some previous owner had left bags and bundles of bat insulation up there, which worked well to build a retaining wall around the outside of the attic, keeping the soffit venting clear.

 

[SpatiallyAware]

Most of the time the chimney has some sort of flashing to keep the blown-in away from it, if not you should install some. Then use silver tape to seal up the seams, but I really can't help you with getting insulation directly up against the chimney itself.

I recommend going through and using plywood to build a backing plate near any eaves/soffits/vents/chimneys and then filling up while you're messing around with it. Personally I try for 1-2 feet, not sure what the code or recommendation is on that. If you buy ~10 bags of blown-in from home depot they let you rent the machine to blow it for free.

It's a two person job to use the machine, one person to blow it around and another to fill the machine. I like having a third crawl around to make sure the vents are open.

 

[Squisher]

You might find the snow melt around the chimney is from the heat in the chimney and any insulating is not going to stop this, unless you see some areas in the attic around the chimney that are missing some or all of the insulation.

 

[olds]

You might find the snow melt around the chimney is from the heat in the chimney and any insulating is not going to stop this, unless you see some areas in the attic around the chimney that are missing some or all of the insulation.

I am thinking, this.

 

[Homerboy]

*** I should note, this is NOT a "fire place" chimney. It is simply the old furnace stack that now runs the exhaust for the furnace/water heater.

 

[rh71]

do people insulate an attic when the 2nd floor ceiling is already insulated? Contractor said it's not common. Mentioned something about needing air to be able to escape through the attic for a purpose too.

 

[feralkid]

do people insulate an attic when the 2nd floor ceiling is already insulated? Contractor said it's not common. Mentioned something about needing air to be able to escape through the attic for a purpose too.

Top floor ceiling, attic floor...same thing.

No one here is talking about insulating the roof joists.

 

[3chordcharlie]

Most of the time the chimney has some sort of flashing to keep the blown-in away from it, if not you should install some. Then use silver tape to seal up the seams, but I really can't help you with getting insulation directly up against the chimney itself.

I recommend going through and using plywood to build a backing plate near any eaves/soffits/vents/chimneys and then filling up while you're messing around with it. Personally I try for 1-2 feet, not sure what the code or recommendation is on that. If you buy ~10 bags of blown-in from home depot they let you rent the machine to blow it for free.

It's a two person job to use the machine, one person to blow it around and another to fill the machine. I like having a third crawl around to make sure the vents are open.

You can get styrofoam vent channel things that protect the soffit vents and install easily with a staple-gun.

The machine is super-easy to use, (but it's definitely a two-person job as you said). I got my house done in a weekend, about 2 hours saturday to guard up all the vents, and about 2-3 hours sunday to actually blow in the insulation. Then about 3 hours to clean up the mess, which was mostly my fault If the hose is long enough, you really want to keep the actual machine outside.

I'm sure new construction is subject to code that probably changes regionally depending on prevailing weather. Around here, R-40 and R-50 are the key numbers. Roughly speaking, a foot of cellulose is about R-40+ and about 14" will get you to R-50. It's a little thicker for blown fibreglass. (I needed to add R-40 to my attic to get to R-50). Existing insulation is of course fine, so calculate what you have, to find what you need. Within reason, more won't hurt anything, but there's declining benefit beyond a certain level.

 

[3chordcharlie]

do people insulate an attic when the 2nd floor ceiling is already insulated? Contractor said it's not common. Mentioned something about needing air to be able to escape through the attic for a purpose too.

You would insulate the roof of the attic if it were exposed, cathedral ceilings, or you desperately wanted the storage space. It's way more expensive, not 'ideal' in terms of air-flow, and difficult to achieve the same R-value.

We're talking about insulating the attic floor.

Edit - BTW there is no more cost-effective way to improve the energy use of your house, other than closing doors and windows. You won't have to wreck and rebuild anything, there's lots of room in attics so you can use very cheap product, and with some care you can easily do this yourself.

New windows for my house (they were ancient and drafty) cost 14x as much as adding attic insulation, and had less of an effect on my bills.

 

[rh71]

New windows for my house (they were ancient and drafty) cost 14x as much as adding attic insulation, and had less of an effect on my bills.

We recently had a new dormer built with Andersen 400 series windows which are the better line and even with them we're feeling a bit of the cold when placing my hand near it on the inside. Not as much as the old replacement windows of our previous house, but it is still not completely airtight. As a matter of fact, I made sure they insulated with R21 in the walls and R30 in the ceiling and the room is still cold - with 50F outside and no heat on, it still drops to about 60F inside. I guess I was just expecting too much from the insulation. Does it only keep heat in rather than the cold out?

 

[3chordcharlie]

We recently had a new dormer built with Andersen 400 series windows which are the better line and even with them we're feeling a bit of the cold when placing my hand near it on the inside. Not as much as the old replacement windows of our previous house, but it is still not completely airtight. As a matter of fact, I made sure they insulated with R21 in the walls and R30 in the ceiling and the room is still cold - with 50F outside and no heat on, it still drops to about 60F inside. I guess I was just expecting too much from the insulation. Does it only keep heat in rather than the cold out?

Insulation keeps the warm side warm, and the cold side cold. But windows have very low R-value, all houses have air-leaks, and even well-insulated areas still have heat transfer So with your heating system off, the temperature inside converges with the temperature outside... leave it long enough with temperature in the 50s outside, and you will have temperatures in the 50s inside, too. Better insulation just means this process will take longer.

 

[feralkid]

We recently had a new dormer built with Andersen 400 series windows which are the better line and even with them we're feeling a bit of the cold when placing my hand near it on the inside. Not as much as the old replacement windows of our previous house, but it is still not completely airtight. As a matter of fact, I made sure they insulated with R21 in the walls and R30 in the ceiling and the room is still cold - with 50F outside and no heat on, it still drops to about 60F inside. I guess I was just expecting too much from the insulation. Does it only keep heat in rather than the cold out?

Hopefully what you are feeling is cold radiating from the window pane. This is normal. If you are feeling a draft, you've got problems.

 

[DominionSeraph]

Hopefully what you are feeling is cold radiating from the window pane. This is normal. If you are feeling a draft, you've got problems.

It'd be a draft if he can feel anything at those temperatures. No way should he be feeling anything with any modern window. Our 1970's double-hung aren't bad enough that we'd be noticing anything in the 50's. (We do have a bathroom casement that leaks like a sieve, and there you'd be able to feel it.)

 

[Red Squirrel]

The chimney should be cold to the touch if it's properly insulated. Is this an actual chimney like for a fireplace, or is it a metal duct? Either way, it should have built in insulation that completely blocks the heat from escaping. I can nearly burn myself if I touch the pipe coming out of the water heater, but if I touch the chimney part just above, it's cold.

That said, I would roll some of that insulation around that area, try to get it snug. Before that though, ensure there is proper vapor barrier and any source of air leakage is blocked. Insulation is to block heat transmission through objects, if there's a big hole and air is let through, insulation wont do anything for you. Vapor barrier is very important.

Try to get around R60 in the attic. That's usually the rule of thumb. More even better. Normally 3 layers of fiberglass is a good start. First the joists, than criss cross then criss cross again. Oh and wear a mask or you'll be coughing your way out of there pretty fast.

 

[3chordcharlie]

The chimney should be cold to the touch if it's properly insulated. Is this an actual chimney like for a fireplace, or is it a metal duct? Either way, it should have built in insulation that completely blocks the heat from escaping. I can nearly burn myself if I touch the pipe coming out of the water heater, but if I touch the chimney part just above, it's cold.

That said, I would roll some of that insulation around that area, try to get it snug. Before that though, ensure there is proper vapor barrier and any source of air leakage is blocked. Insulation is to block heat transmission through objects, if there's a big hole and air is let through, insulation wont do anything for you. Vapor barrier is very important.

Try to get around R60 in the attic. That's usually the rule of thumb. More even better. Normally 3 layers of fiberglass is a good start. First the joists, than criss cross then criss cross again. Oh and wear a mask or you'll be coughing your way out of there pretty fast.

Vapour barrier is important - I'm assuming that is already in place. If it isn't, then there are decisions to be made! Keep in mind that in older houses many coats of oil-based ceiling paint will actually act as a vapour barrier.

I'm having trouble thinking of an attic that I would rather insulate with batts than a blower though, based on time, but mostly on cost.

 

[Red Squirrel]

Blower is fine too, just be sure you have baffles so you're not blocking the eves. Batts are easy for DIY as you don't need specialized equipment or a pickup truck. But if you have a pickup truck then you can rent the equipment. The blown is also more efficient, less air gaps and more uniform.

 

[3chordcharlie]

Blower is fine too, just be sure you have baffles so you're not blocking the eves. Batts are easy for DIY as you don't need specialized equipment or a pickup truck. But if you have a pickup truck then you can rent the equipment. The blown is also more efficient, less air gaps and more uniform.

For a 900sf attic (the same as mine) I'm coming up with ~$1000 for batts vs. ~$550 based on Home Depot pricing. That's to add R-40 to whatever is there. I see they have indeed updated the magic number from R-40/50 to R-60, too. To me that's enough savings to beg, borrow or steal a truck long enough to do the job