Additional attic insulation???

[Stubby]

My heat bills are about twice what neighbors pay in similar houses. And, I get ice dams. So it seems there is heat leaking up into the attic. I have soffit vents and a ridge vent. So I called 3 insulation contractors. One said the 6" that is in the attic between the 2x4 joists is fine and that adding more won't make a big difference. Two others wanted to add another 6" of cellulose. Pink stuff is more expensive and doesn't fill nooks and crannies as well.

My walls have 2" insulation which was standard back in 1970 when the house was built. I replaced all the windows with double pane vinyl windows. That was years ago and it did make a difference. I have a large aluminum frame slider that I cover with film for insulation.

I'm hesitant to spend $1600 on additional insulation if it isn't going to do anything. Can anyone suggest what is causing the heat loss? Thanks.

[m Ransley]

6" of insulation is apx R 21, You dont say where you live or your Zone. Im Zone 5 to -20f, code is R 35 but optimal is apx R 50-60+. So unless you live in say florida or zone 9 more will help. What is attic sq ft. your areas low temps and Zone. Ice dams, may be air leaking up from he house, not enough venting, and lack of insulation.

[Doug Kanter]

If the pink stuff is cut correctly, there's no reason it won't fill the spaces nicely. I haven't priced it in years (but I'm about to, this weekend), so I may be talking through my hat, but wouldn't it be cheaper to use the pink stuff, and install it yourself?

[louie]

Adding 6" of cellulose to the attic will help tremendously, so long as the soffit vents are kept open with some baffles. You'll add an average R value of 3.5 per inch of the cellulose so you'll increase your attic insulation from R-19 to R-40.

Other things you can do is move around your house with an incense stick looking for drafts. Seal up as many drafts and leaks as you can. There are professional services that will install a temporary blower into a doorway and will actually pull air from the house, creating a slight vacuum. Then they will actually test how much negative pressure is created and how much air volume is moving through the fan and from that determine how "leaky" your house is. They usually go around with a smoke pencil looking for leaks while this is happening too.

[CJT]

Which is what, about 3% difference in heat loss?

[scott21230]

The additional insulation will make a difference. Use sheets of fiberglass or blown in biberglass and cover the joists completely. The more the merrier. Also, fix any air leaks. Insulate the hot water pipes and you should be able to turn down the setting on your hit water heater. The walls should be the last thing you try to insulate.

[CJT]

Oh, and that's the heat loss through the attic, which is only a fraction of the whole-house heat loss.

As you can probably tell, I'm skeptical.

[Doug Kanter]

Comfort is related to how quickly heat is being lost, and that's difficult to quantify. But, what if this mysterious comfort goal lies somewhere in that 3%? It would be a shame not to try.

[CJT]

It's only money ...

[m Ransley]

Heat rises, insulating an attic is the cheapest way to save. 3% or whatever loss you figure you save on utilities and increase resale value. Adding 6" or R 21, well next year it will have settled 15-20% and be R

1. I put in R 100 it settled to R 80, an R figure that is optimal not what your local Minimum codes require. Through all I did I cut Ng by

60%, everything has a payback when it comes to insulation since standards do not reflect 1.70 a therm Ng, they are outdated from the 50s.

[Nexus7]

Well, you're losing heat through the attic, so you need insulation there. You should go up there (with dust mask, body all covered, etc.) and check for great big holes into the living space. Once you take care of that, you can do your own cellulose for less than $200 per 1000 sq ft. Just don't cover up your vents.

[yourname]

But you are wrong. Since heat rises, especially in hot air heated houses,

the temp differential is much higher on the ceiling than on the wall. There is absolutely a point of diminishing returns, but if you do a real heat loss analysis on your house[it is not difficult, a pocket calculator is helpful, but not required] you will find that half the heat goes out the windows, and half the remaining goes out the roof. SO if you take that[gross] generalization, and you burn 1000 gallons of oil a season, figure 250 of it goes out the ceiling. At 2.50 a gallon that is 625 A SEASON. Are you betting on a return to 90 cent a gallon oil? I'm not. lets say with these made up numbers you have r20 in the attic, the numbers tell you that it should save you 125 gallons a year by going to r40.

[PipeDown]

2X the neighbors. Maybe you have a leak in a heating duct and you are pumping warm air diectly into the attic. A little duct tape and some duct insulation might give you a bigger bang for the buck. Go up on a cold day while the heat is running and look for a duct leak. This would cause massive inefficiency and ice damming, mimicing heat loss through insulation.

If you do not have forced air heat with ducts in the attic, disregard this advice.

[Stubby]

Even the Energy Star house survey guy recommended against insulating the water heater. That was a good idea back before we had the good insulation we do now days. Around here (Chelmsford,MA) waterheaters only last about 6 years because of the minerals. So I'd have to buy a new waterheater blanket with every replacement. The heat loss won't pay for it.

[Stubby]

Right. At least two of the contractors said they would install "proper vents". These are the styrofoam vents that allow air to enter the soffits and head up to the ridge vent. It should carry away heat coming out of the ceiling.

I would do the job myself, but I'm too old, too fat and too stiff.

[Stubby]

Right. I have forced hot water in baseboard heaters around the edge of the house.

However, there is an analagous situation to a leaking hot air duct. I used to have hydronic heating with hot water circulating through a copper pipe embedded in the concrete house slab. It was great heat but (a) after 30 years the lime in the concrete ate pinholes through the copper and (b) in 1970 they couldn't care less about energy and builders didnot put styrofoam insulation under the slab. So, I was doing my part of globe warming! Some people lose hot water from their heating systems. It costs a lot and they don't know it's happening. But I'm not losing heat that way anymore because I abandoned the hydronic system and installed a baseboard loop.

[w_tom]

Some obvious heat leakers. Windows. One a windy day, curtains still should not move. For that matter, no place anywhere in the building should feel air motion when outside wind blows.

Other less obvious leakers. In the 1970s, contractors would routinely say that insulation on outside wall between floors was unnecessary. Easy to identify that myth. Floors on inside rooms are cold. Same applies to the space above foundation; where 1st floor joist meet on the outside wall. Sill plate on foundation - did they forget to put a fibrous insulator between foundation and first wood? Drafts at the top of a foundation on windy days identifies bad construction (that is quite legal). 2" insulation inside walls is classic pre 1980 thinking. It should be at least 3.5" inside all exterior walls - including places where interior walls join to exterior walls. Today, most contractors still will insist insulation in corners is not necessary. Furnace - where does cold outside air come from to burn in the furnace? Does it use interior air?

Heat ducts - > My heat bills are about twice what neighbors pay in similar houses.

[Stubby]

I don't like the idea of laying more batts 90 degrees to the existing ones. But that was suggested. Blowing in "pink stuff" (fluffy loose fiberglass) is preferred.

[Stubby]

I think it will be more than a 3% saving. Say the temp difference from inside to outside is 50 degrees. The heat flow with R19 insulation is

50/19 = 2.6 in some arbitrary units like BTUs per fornight. With R34 the loss flow will be 50/34 = 1.8 in the same units. So in some amount of time the heat lost will be (2.6-1.8)/2.6 = 0.31 or 31 per cent less.

[Nexus7]

The "proper vents" are just plastic or styrofoam channels that staple to the roof deck. The plastic ones should be more durable in that they won't have to be handled as delicately during installation. Depending upon the way the edges of your attic space adjacent to the soffit vents are laid out, these vents may not be necessary, if the insulation will stay away from the vents. Maybe you could supervise the job and have some friends blow the cellulose. Between beer & pizza you'll spend a lot less than $1600.