ice dams

[mrbeanfan]

I live in Minnesota. I have a story and a half house (basically, two bedrooms exist in the attic.). Every year I get nasty, nasty ice dams and I am trying to get ahead of it now.

Here's my question: The previous homeowner had insulated kneewall where the highest part met the room walls. All the way to the top. There was NO AIR going up over the insulation to escape out the three or four roof vents. Completely sealed off. No wonder my upstairs gets to be 100 degrees in the summer.

I ripped that out. I would like to cut in some soffit vents but I have a tiny (5" overhang).

Are soffit vents going to do me any good? What about a "Whole house fan" especially in the summer? Did I do the right thing taking out the insulation batts at the top of the kneewall connection so that air can move up to the vents?

Another thing that I thought of is my boiler (located in the center of my home) puts out a huge amount of heat. It rises right through that ceiling, right through the floor above, and right to the roof, where it consequently melts a lot of snow.

Would I be doing the right thing by lining the ceiling in the boiler room (it's a small room) with R 21 insulation, 1/2 sheetrock, followed up by some 1" R-Board? My goal is to keep that heat downstairs and not flying right to the roof every time the boiler runs.

any suggestions would be appreciated..

mrbeanfan

[tbasc]

Insulating the boiler is a good idea. I would put gypsum board between the insulation and the boiler for fire protection.

It sounds like there is inadequate insluation above the bedrooms, given they are hot in summer and melt snow in the winter. I'm not sure venting will solve your problems. The Building Science Corporation web site has a section "venting on venting" which is useful. TB

[mrbeanfan]

Hi thanks for the reply. i had planned on R-21 between the joists in the boiler room (its a tiny tiny room) Over that with 1/2 sheetrock. (i am assuming you mean this when you say "gypsum" Over that with 3/4 or 1 inch R board.

The insulation above the bedrooms seems sound. I peeked up there from behind the kneewall and it looks sound. looks relatively new actually or within 10-15 years old.

I did make some temporary "baffles" to channel air up to the roof vents (there are three on one side of the house plus a gable vent at the top of the attic.

I will check the builder site you recommended.

[e-mail] wrote:

[Dano]

Your issue is a combination of insulation and venting. The ice dam is caused by your attic air being warmer than the outside air in winter. The warmer air melts the snow which runs toward your eaves which of course are surrounded by outside air. The snow melt hits the colder eave and freezes. In a short time this builds up and holds water back behind it. As the typical shingled Minnesota roof is not designed to hold water - the water leaks into the house.

Now, I don't know if you need more insulation or more venting - but the goal is to keep the attic air the same temp as the outside air in the winter.

[mrbeanfan]

well, i think the previous owner has placed some sort of membrane up there because we do not get any leaks, thank goodness. but it is hard on the roof and unsightly. Plus, no gutter system will stay up because the glacier will take it down.

I have no soffits.

I do have vents in the gable (4 total) which vent the kneewall area both sides, north and south. I also have 2 vents at the top of the attic area. But the previous owner had plugged all the cavities which would allow air to flow through to the top.

I removed each of those little plugs of insulation but the insulation goes right to the roof deck in most cases.

Dano wrote:

[kevin]

This will obviously not help your ice dams.

First, as another poster pointed out, and you seem to have missed, it is probably a very bad idea to leave 1"R-Board exposed above a boiler. It is not fire resistant in the least, and as far as I know, is flamable. Put up whatever insulation you want _first_ (R21 +

1"R-board), and then _cover_ it with the 1/2" sheetrock. Thus, no exposed insulation above the boiler.

I also wonder in general about your whole idea here. Is your house too hot in the winter? Then turn down the thermostat. Do you spend a lot on heating (i.e., suspect too much heat escaping out the top)? Then insulating the boiler room isn't going to help -- the heat will still go out the top. That extra heat from the boiler has to go somewhere, and the only place it can go is into your downlstairs. Or you could send it directly outside. But then you would have a colder house, and you'd have to burn even more to keep it the same temperature, at which point you will be losing just as much out the top as before (in additoin to burning more fuel).

So -- forget about the boiler. Instead try to keep the heat where you want it -- inside the house, preferably in the rooms you use most (downstairs).

We have a similar setup in our house. One thing the original owner did was to put a door on the stairs going to the bedrooms. We close this in winter, and also adjust the heat vents, and can drop the temperature upstairs by several degrees (by keeping the heat downstairs). This saves fuel, and reduces the ice dams. Be careful of lowering the temp too much (condensation, mold, etc., become a problem at some point).

-Kevin

[Lawrence]

It seem like adding vent to the attic could only help.l

I live in northern Minnesota. I have also lived down south. I assume you are talking about an attic fan which exhaust the whole house. Those are common in the south but I have never seen one in my 22 years in Minnesota and I do not think they aer suited to a climate where we heat our home 8 month of the year. It would likely contribute to any ice dam problem since it creates a large opening in the ceiling for the fan.

Hard to say. Less insulation in a wall could actually contribute to the problem.

It couldn't hurt but as others have said, use gypsum drywall for fire protection. dont' leave insulation exposed to the boiler.

Many, many homes in minnesota have ice dams. They are pretty much the rule in some older neighborhoods. My take on it is that it is a lot easier to design and construct proper attic venting in a new construction. It is quite a lot more difficult to do so in an older home which may not have been properly designed for ventilation and where previous remodels and upgrades may prevent you from doing so.

By all means do what you can to prevent the problem but don't be surprised if you wind up in the same boat as many others, with ice dams. My place has them. I actually gently remove the snow from my roof after a storm. then when dams do form, I go up there with ice melt and sprinkle above the ice. there are also ice melt bags that folk place above the dam and it releases the chemical gradually. I also understand that some use electric cable to melt the ice. Some just ignore them but they can cause your roof to leak, damaging your roof deck, attic insulation and in the worst case leak into the house. It you can go into the attic to see if it is leaking, it might save you some work. Ice dams are undesirable, for sure, but they are not always easily fixable. Monitoring and Managing the situation on a season by season basis is what you may be stuck with.

lawrence

[MDT at Paragon Home Inspection]

Preventing "ice dams" involves a lot of factors, for example here's an interesting "case study":

It can be very difficult to prevent ice dams at roofs and soffits when knee walls separate conditioned living and unconditioned attic spaces, IMO one alternative to consider in such situations are correctly installed "industrial" grade variable-resistance heating cables extending into the gutters and down the downspouts, for example:

Done properly this not only addresses the "roof" related problems, but also the secondary problems of ice-clogged gutters and downspouts.

These are not an inexpensive solutions - for starters they generally require at least one dedicated electrical circuit to the roof area - and they address the "symptoms", not the "causes", but OTOH you know going into the project that if done properly it *will* solve the problem, which is almost impossible to guarantee in advance for other approaches.

(For the record, I have no connections of any kind with any of these companies making such products).

Michael Thomas Paragon Home Inspection, LLC Chicago, IL mdt@paragoninspectsDOTcom

847-475-5668

[TakenEvent]

How old is your house? Are the attic rooms the result of remodeling or were they part of the original plan? Typically, the easiest way to vent finished attics is by running proper vents from soffit vents to a ridge vent. It's surprising that this wasn't accounted for when the house was built (depending, of course).

My Dad's house is over 100 years old. It has a partially finished attic, with kneewalls containing bookshelves running the length of both sides. Both sides also have an access door. Here's what I suggest for you, based on what I did at my Dad's house.

Make sure the tops of the first-floor walls are covered by the attic insulation. The tops of walls are a source of heat loss, even though the walls contain insulation. Trust me on that. If you have no soffit vents, there is no air from the soffits to worry about. Tuck that insulation back in there, without crushing it too much, of course. Insulation works by way of its thickness. Cover the floor area (or the area between joists) behind the kneewalls with insulation. A second layer probably would help.

You'll want a way for cold air to get in, say gable vents or soffit vents. My Dad's house has soffit vents, unlike yours, but it also has gable vents (leading to the area behind the kneewalls) on both ends of the house, behind both kneewalls. If you don't have those, you should fix that. Without some form of gable or soffit vent, the heat from your house will pool behind those kneewalls, with no source of cold air to replace it, and nowhere to go but through the roof, which makes ice. Make sure that the vents are not blocked by insulation. While it is important that the hot air has someplace to go, it won't go very fast if there is no incoming air to replace it.

The heated air needs someplace to go, so there should be proper vents running up over the kneewalls to a ridge vent. Make sure the tops of the kneewalls are covered with insulation, and also insulate the kneewalls themselves. If you have access doors or panels, glue pieces of rigid foam insulation to them.

Since your attic is finished, those standard solutions may not be financially viable options at this point. You won't get those proper vents in place without serious surgery. You may want to look into a solution involving those zigzagging heater cables or roof flashing. The roof flashing has a bit of a dated look, but you'll hardly notice the heater cables after a while.

The following link may help you as well.

[mrbeanfan]

The house was built in 1950. The current rooms were always there I believe.

I do have gable vents at the end of each "kneewall" area, and one at the very top of the attic.

This is what it looks like

x x x x x x x x ------ x x ____ x xxxxxxxxxxxxxx x x

The area inside the triangle on the one side of the house is used for storage. Up the straight portion is insulated up to where the wall meets the angled ceiling. I pulled out the very top part so that air can rise to the roof vents (there are three box vents on the very top.

What do you mean by "proper vents" running up over the kneewalls?

It seems cooler upstairs today after removing that insulation..

TakenEvent wrote:

[MDT at Paragon Home Inspection]

from soffit vents to a ridge vent.

There's been a lot of research into ventilation in the last decade, the upshot of which is that it appears that a lot of what "we all knew was true" probably isn't.

For instance, take a look here:

If it's in fact that case that most attic ventilation in the above scenario is cross-soffit, then the standard approach for venting past knee-walls - allowing a space in the rafter cavities for airflow above the insulation and assuming that convection is going to move the air up from the soffit to the ridge - is probably a lot less effective than we been taught to expect.

Michael Thomas Paragon Home Inspection, LLC Chicago, IL mdt@paragoninspectsDOTcom

847-475-5668

[TakenEvent]

Proper vents are basically styrofoam chutes that keep insulation from blocking airflow. By using proper vents, you can keep the top of the wall insulated while maintaining airflow to the roof vents.

[TakenEvent]

[...]

Here are some links with pictures that will make everything much more clear.

[TakenEvent]

vents from soffit vents to a ridge vent.

That article is from 1993 - not that that means anything, necessarily. I've personally seen proper insulation and ventilation make dramatic differences in houses with ice problems.

Due to the design of his house, the OP doesn't have much choice in the matter unless money is no object. Either he does what little he can, and recoups some of the energy costs that will be increasing upon the placement of the new heater cables, or he's on a ladder with a heat gun, an extension cord, and a hammer come January 31.

[MDT at Paragon Home Inspection]

To be clear, I'm certainly not trying to suggest that attic ventilation does not make a difference, especially as regards moisture control. Every home inspector sees numerous examples of veneration and moisture control problems in attics, and there is no question that improved ventilation can often help correct such problems.

Rather, my point was that you can't just assume that actual houses are acting like the examples commonly depicted in of diagrams "attic ventilation" under simple gable roofs, or that seemingly "similar" systems act in "similar" ways.

For example, if you are depending on convection in rafter cavities to move air from lower in the attic and up past knee walls to a ridge vent in order to lower the temperature at the roof sheeting near the eaves

- a situation where you can't get the sort of cross-soffit ventilation depicted the link in the post above - it's probably especially important to pay attention to providing sufficient soffit vent area, making sure every rafter cavity is vented, that you are using one of the "engineered" ridge vents specifically designed to assist in exhausting air when wind moves across it, and so on.

And, for example, to be aware that in some cases (ex: rafter cavities obstructed by cripple jacks or below dormers):

you just can't ventilate the eaves via flow up to a ridge vent.

Homeowners not aware of such issuers are more likely to be frustrated in their attempts to deal with problems such as ice dams.

Michael Thomas Paragon Home Inspection, LLC Chicago, IL mdt@paragoninspectsDOTcom

847-475-5668

[TakenEvent]

The OP doesn't have ridge vent or soffit vents. He just has a few He may or may not find it beneficial to install a ridge vent, depending on the airflow up through the rafter cavities. If there is no air getting to the ridge, the ridge vent is worthless. The impression that I get, based on his description, is that there is also a cavity above the attic rooms which is vented by a gable vent and some roof pots. The question becomes one of ventilating the lower cavities.

If there is no good way of getting the warm air to the vents up above, then perhaps installing a couple of roof vents above the lower cavities would be the best solution.

[TakenEvent]

Make that, "He just has a few roof vents up top."

[jian.m.ren]

Hi; I have a solution for the ice dam problem. My solution does not remove the ice dams, but it eliminates water accumulation above the dams, and it prevents leaking due to the ice dams.

I am a Ph.D. in chemistry. I lived in Montreal, Canada for more than

10 years. I invented/found the solution when my house had ice dams. The solution is simple and inexpensive. It does not use any electricity.

For a fee (~$100 USD ?), I can provide a kit and instructions on its installation. You would need to install it on your roof.

Thanks and best regards.

James Ren Boston, MA, The previous homeowner had insulated kneewall where the highest part

[Al Bundy]

[e-mail] wrote in news: [e-mail]:

Don't tell me. Shoot a tarp over the roof with a whaling harpoon.