BS: House insulation question

Subject: BS: House insulation question
From: Donuel
Date: 29 Oct 05 - 11:41 PM

Regarding those little window vents that ventilate attics as well as the roof fans...

Should people seal those up tight during the winter?

I know they may help in strong wind storms to equalize pressure under the roof but it seems that closing them off during cold months would help insulate the ceilings below the roof.

I have 4 of those attic vent windows. Coild there be anything wrong with a warmer attic?

Subject: RE: BS: House insulation question
From: Bert
Date: 29 Oct 05 - 11:53 PM

Depends where you live. If it's very humid you might want to leave them open.

Subject: RE: BS: House insulation question
From: Ebbie
Date: 29 Oct 05 - 11:59 PM

I manage some rentals. After one renter moved out, I discovered he had taped up the vent in the bathroom (about 8 inches square). There was mold from ceiling to floor.

Subject: RE: BS: House insulation question
From: Naemanson
Date: 30 Oct 05 - 12:33 AM

Leave the vents alone. They help with a whole raft of things from equalizing pressure (though IMHO that reason is overblown), to keeping the house dry. If you are worried about the cold add another layer of insulation in the attic. You want air to flow through that section of the house.

Subject: RE: BS: House insulation question
From: JohnInKansas
Date: 30 Oct 05 - 01:30 AM

Generally the roof vents should be left open. Even in winter, the roof is cold enough to produce some condensation, and wet insulation is useless.

Unless you're on a slab directly on the ground, you'll probably find "crawl space" vents just below the ground floor level as well. In most areas, it's okay - and usually recommended - to close them during cold weather. The ground under the house has lots of thermal capacity, so even without ventilation you don't have a large hot/cold gradient to cause condensation.

If you have known "wet ground" under the structure you would of course want to leave some underfloor ventilation; and in some areas with peculiar (unusual, not necessarily bizarre) weather leaving some or all of the underfloor vents open may be advised. A good local heating and airconditioning service place probably would advise you without the need for a service call and fees.

Roof vents are seldom made with closure devices, at least in areas where I've lived. The exception might be if a "whole house fan" was installed that required additional venting when it was in use, in which case a specially added vent may have closure devices.

Underfloor vents usually have a lever or rod for opening and closing. If there isn't a mechanism, the builders probably thought you wouldn't need it (or it may have fallen off - they're usually pretty cheaply made).

John

Subject: RE: BS: House insulation question
From: Barry Finn
Date: 30 Oct 05 - 01:35 PM

The attic vents (type you're mentioning) are almost useless but better than nothing. I take it that you have insulation on the floor of your attic, adding there is your best bet along with increasing your ventalation. The best situtation you can have is for the attic temp. to be the same as the outside, this will stop most condensation which will soak the insulation at the wals, overhangs (soffits) & attic floors. This will also protect you from ice dams. An ice dam is caused by the snow on your roof melting during/from the days sun & the heat build up inside the attic. The snow when it melts from both will is suppose to run off your roof but depending on how the house is insulated & vented it may get to the edge & refreeze (this is 1 of the reasons why you'd need soffit vents at the edge or at the roof overhang) on the surface thus trapping the melted water running down the roof & then getting trapped between the ice surface & the roof covering. Here's where it pays to have an ice & water barrier (or called an ice & water shield, a rubber self adhearing sheet usually 3'x65') that runs a min. of 3' up the roof from the warm outside wall (not from the roof edge) meaning that you'll do best with at least going 2 sheets wide. & using at least a full sheet going up the verticial edges & at least 1/2 a sheet going up the any doma walls turning the sheet at least 4" up at the wall transation & using 3x3 patches around pipes, chimneys &other protrusions. The best in non electric roof vent is the type that sits on the peak of the roof & runs it's lengths saying a min of 3' foorm edges & chimneys. this type of vet collects all the heat build up that travels up the attic underneath the roof sheating (usually roof decking or 5/8 or thicker plywood) & between the roof rafters. An ideal roof if putting on a new on would be to 1st cover the roof with a vapor barrier 6mil plastic sheeting cover that with a solid sheet of insulation at least 2" (3"+ is much better) thick. This type of insulation would be sheets of poly-iso & the bottom (or the surface that would lie on the roof over the plastice) would have been fabricated with air channels to allow the air to flow up the roof between the insulation & the plastic & the top side of the insulation would have an adheard sheet of plywood or os board (oriented stand boar) 1/2" or better thick, the apply your roofing material (if you used a shingle & I'm assuming you're in could country, do not use a fiberglass shingle use an asphalt only shingle. The fiberglass shingle gives you a higer fire rating but can't take the constant change bewteen freeze & thaw light they can in warmer climes (you would have as many problems in warmer climes either). Lastely in all roof valleys in cold climets they should be closed, meaning no metal valleys & no valleys made from from a roll material only from shingles that over lap each other with at full 3' wide sheet of ice & water shield under lying it. A little bit about the soffit vent here.The soffit vents need to be placed at the botton of the roof under the overhang, spaced so that there's at least 1 vent per roof rafter that way the air can flow up the underside of the roof between rafters,that could be up to 10" deep,(at trap for moisture & heat that normally isn't taken care of by other types of ventulations) & escape thru the roof vents(I didn't menttion that these vents shuld be the shingle over types & not the metal types. I hope I gave a proper & coherent discription or all this. Please feel free to PM me with any questions or explainations.

Barry

Subject: RE: BS: House insulation question
From: GUEST,leeneia
Date: 30 Oct 05 - 06:11 PM

A friend of my took a tour of her neighborhood, talking to those who had the fewest icicles and roof dams. Those whose attic was the same temperature as the outdoors had houses in the best condition.

Subject: RE: BS: House insulation question
From: Deckman
Date: 30 Oct 05 - 07:06 PM

What country/climate are you in? Bob(deckman)Nelson

Subject: RE: BS: House insulation question
From: Donuel
Date: 01 Nov 05 - 09:36 AM

Whew, the expertise in the answers blew me away. The roof overhang is over 3 feet and have no soffit vents ( if I grasped the concept of an under roof vent correctly )

There is only about 8 inches of loose insulation which doesn't seem like much for the DC area which can sometimes get below zero

With the above advice...
I plan to leave the vent windows alone.

My plan now is to lay 9 mil bubble wrap ( a former solar pool cover ) between the rafters of the second story roof and then put some new insulation rolls down with the "wooly" side up on top of the bubble wrap.
I figure that condensation will be wicked away from the wooly side more efficiently than from the silver side.


I can not safely get into the first story attic wing, so that will have to wait for professionals.

Fiberglass Insulation is nasty stuff and requires it never gets into your lungs.

Subject: RE: BS: House insulation question
From: Jeri
Date: 01 Nov 05 - 10:26 AM

Donuel, I think putting bubble wrap between the attic floor and the insulation would trap moisture and might lead to growing a nice crop of mold at the very least. Comments by people who know?

Subject: RE: BS: House insulation question
From: Deckman
Date: 01 Nov 05 - 11:46 AM

Donuel, I AGREE completly that putting "bubble Wrap," which is plastic faced, in there would be a BAD IDEA. Insulation is strange stuff. It has to insulate against temp changes, and breathe at the same time.

As for fiberglass insulation, I feel that the dire warnings about using it are highly overstated.

Hope this helps, Bob

Subject: RE: BS: House insulation question
From: gnu
Date: 01 Nov 05 - 12:33 PM

Bubble wrap is a vapour barrier and such should always be on the warm side of the insulation and NEVER anywhere else.

There is a great deal of excellent advice above. I would add one comment regarding ridge vents (vents running along the roof ridge). A few years ago, after seeing a large number of problems in houses with such vents (I was a "home inspector", among other jobs, for 8 years), I researched the specs on the three most common ridge vents sold in my area. I was surprised to find that air flow per lineal foot varied threefold from the "min to max"!!! The only houses that did anywhere near well with ridge vents were rooves with a pitch over 4/12... cathedral configurations with pitches over 4/12 and ridge vents were still a problem. Small, off-the-shelf ridge vents suck.

Subject: RE: BS: House insulation question
From: JohnInKansas
Date: 01 Nov 05 - 12:53 PM

Donuel:

Definition 1.

raf•ter    (raf‚tƒr, räf‚-) n.1. any of a series of timbers or the like, usually having a pronounced slope, for supporting the sheathing and covering of a roof.

Definition 2.

joist    (joist) n.1. any of a number of small, parallel beams of timber, steel, reinforced concrete, etc., for supporting floors, ceilings, or the like

The horizontal beams that support the ceiling below are JOISTS, not rafters.

The (usually slanted) beams that support the roof sheathing and the roof itself are the RAFTERS.

When talking to the professional from whom you really should get advice on your own specific situation, you may want to emphasize that you know which you're talking about, by using the terms Roof Rafters and/or Ceiling Joists.

The non-permeable sheet material that's placed on one side of the insulation is to prevent moisture from condensing in or on the insulation. Wet insulation has virtually no insulating effectiveness, and in addition will probably support very nasty molds and mildew. Most insulating materials do not support problem growths, but the dust that inevitably accumulates will, if there's moisture retained in the insulation.

If you meant that you intend to add more insulation on top of existing insulation between the ceiling joists, there should already be a vapor barrier under the existing insulation. You would need to pull up enough of the existing stuff in a few places to make sure. Fiberglass batt/roll type insulation nearly always does have a barrier, since it's part of the batt. Loose fill insulation like cellulite or vermiculite sometimes will be found without a barrier, but that's only likely in rather old buildings.

Adding a second vapor barrier would potentially allow moisture to accumulate between the two barrier sheets and you could end up by making the existing insulation completely useless. Even if you don't accumulate enough moisture in the old insulation to destroy it's ability to block heat flow, you may produce a breeding place for mold and mildew between the two barriers.

Fiberglass insulation is usually supplied in rolls with a "paper" backing applied to one side of the insulation. The "paper" is an effective vapor barrier, and in situations where you need a barrier you should not normally attempt to "add a little extra." Use the paper on the roll. When installing more than one layer of fiberglass roll or batt insulation, or when adding over existing insulation that already has a vapor barrier, it is normal practice just to "slit" the vapor barrier, making large "X-shaped" cuts, so that only one barrier remains. A box-knife or similar tool makes an effective "slitter."

Fiberglass in roll or batt form is not generally considered an extreme "breathing hazard" but you should use a properly fitted and effective breathing filter. Any attic or other "closed off space" will have sufficient accumulation of dust to make the dust a significant breathing hazard with even minor disturbance. Since it's impossible to tell what might be in the accumulated dust I might stick my head through a hole to look around, but I will not enter an old attic without at least a disposable filter mask. Others are less cautious.

For prolonged work in such spaces it's difficult to maintain a secure fit with the disposable masks, so I'd strongly urge that you spend the $10 (US) bucks or so for a good rubber mask with replaceable filters and adjustable headbands.

Be aware that if you add ceiling insulation that covers all the joists, you will have rendered the attic virtually inaccessible for any purpose. If you can't see the joists, you can't tell where it's safe to step. If you step anywhere except on a joist, you risk punching a hole in the ceiling below. If there is heating/cooling/ventilating ductwork in the attic you may want to leave a path of exposed joists for access to the ducts - if you expect to do your own work on them. An alternative is to add "walker boards." If you'd probably leave any work there to professionals you can let them figure out how to get to stuff, and they probably will.

You shouldn't have any real difficulty finding a web site by one of the insulation suppliers that will give you accurate guidelines for installing - and for proper vapor barrier placement. Since you're the one who knows exactly what your situation is, you should be the one to do that research.

John

Subject: RE: BS: House insulation question
From: Donuel
Date: 01 Nov 05 - 01:09 PM

Joists, yeah that's the ticket...

ahh heck I guess I'll leave the whole thing for when a new roof is installed next year. Still there is lots of interesting stuff here.

Subject: RE: BS: House insulation question
From: JohnInKansas
Date: 01 Nov 05 - 08:56 PM

Donuel -

You should be able quite easily to check out what insulation factors are recommended for your local conditions. "Frequently below zero" isn't generally considered extreme, and the cost and inconvenince of "excessive insulation" may make it more sensible to pay the bill for the bit of fuel that might be saved - even at the higher heating fuel rates being predicted now.

Even your local weather service may have "fuel degree days" averages posted that can be used at insulation makers' sites to make reasonableness estimates.

People often think of adding attic insulation because it looks easy, but the insulation in your exterior walls, and/or thermal leakage at windows and doors, often limits how much you'll benefit from "exceptional" amounts in the attic. It can be like putting a thicker cork in the little hole, when there's a big hole right next to it. The bucket still leaks at about the same rate.

John

Subject: RE: BS: House insulation question
From: Cluin
Date: 01 Nov 05 - 09:25 PM

Don't forget to clear the eave vents and install rafter baffles to ensure air flow through the whole attic. Your attic should be cold as outside during the winter.

Subject: RE: BS: House insulation question
From: gnu
Date: 02 Nov 05 - 05:57 AM

www.carsondunlop.com sells "The Home Reference Book". Check it out. I highly recommend it.

Come to think of it... I still have about thirty of them in the garage. Anyone want one at say, $30 plus shipping, Canuck bucks?

Subject: RE: BS: House insulation question
From: Barry Finn
Date: 02 Nov 05 - 03:57 PM

Hi Donel,

If you're going to wait until next year & have the whole system installed by a pro a couple of important things to look & ask for. 1) cert of insurance, if some one gets hurt you don't want them owning your home. 2) Venting system, get rid of the windows & install ridge vents, shingle over style. Metal vents takes a good bit of care installing which most take short cuts on & the design is poor. They shoulf be installed with in a bed of sealant then fastened with rubber gasketed screws seams sealed, ends plug & the baffels bent of cut so as not to form a dam for standing water(if you've got a hip roof ridge vents can also run up those too. Soffit vent under the eaves min of 1 (they come in 1,2 or 3" round)round vent in between each rafter or install a long soffit vent that runs the entire length of the eave (best option-more air flow). Make sure that the roof decking at the peak is cut back to approx 1/2" to 3/4" to allow the vent to work3) Insulation system, install a moisture barrier of 6mil plasic(fire retardent if you can afford it)as said above install always on the warm side. I'm not to keen on fiberglass but it not bad either, I'd perfere to install 4x8 or 2x8 sheet of poly iso, higher R value easier & safer to work with, IMO, cleaner. 4) Ice & water shields at the eaves should run at least 3' past the the warm wall, so depending on he pitch it would be normal to run a sheet & 1/2 to 2 sheets along the eaves a large overhang may require more, at least 1/2 sheet along the outside vert roof edges, around pipes or other protrusions install a 3' square patch around chimney's, skylights, domas a 1/2 sheet will do but run a min of 4" up the sides or vertical & in all valleys install a full sheet. Do not cover the roof entirly with a barrier the roof does need to breath (the benifits of slate, clay or tile). 4) the roof sysem should be a decent quality shingle, in cold weather areas a 30yr. asphalt shingle (non fiberglass) should be used. The life of a fiberglass shingle is about half of it's rating in cold areas theres no play in them & they eventully crack or split from the constant freeze thaw cycle. When installing on a roof with a 4 1/2" pitch or less (3" pitch is hardly exceptable, unless cutting down the headlap size from 5"to 4", even then not a good idea) install by what's known in the trade as 'hurricane nailing' that's 6 nails per shingle in lieu of 4 nails this also goes for high wind ares. Becareful of those who nail shigle in a vert style, you need to leave the end nail out to side the shigle in the next up coming row & a lot of roofers won't take the time to lift & nail the loose end as they go by it, hence you see little fishmouths (bumps in the edge of the shingle) every other course going verticall up the roof. Removal of the existing roof(s) is always the better way to go. You get to renail any place that needs it, replace any sheathing that needs it, if the substrate is week or not thich enough (5/8" 5 ply plywood min, I do not recommend any other type of 4x8 sheet) or 3/4" lumber depending on the spacing of the rafters 16" or 24" on center is the norm. At this point it is easier to sister any rafters that may be cracked, install or reinstall skylights properly, update step & pipe flashings, counter, base & chimney flashings. It decreases the weight on your roof structure, important for those in heavy snow zones. For wind rating google up national wind zone maps to find out your area Good Luck & let us know what your plans are.

Barry

Subject: RE: BS: House insulation question
From: number 6
Date: 02 Nov 05 - 10:04 PM

gnu ... if I ever get up yer way I'll certainly buy one.

sIx

Subject: RE: BS: House insulation question
From: GUEST,Rome
Date: 11 Nov 05 - 01:49 PM

I am thinking of having my walls insulated. This is a free service for pensioners in England. Are there any disadvantages to having a house insulated or is it all advantages!

Subject: RE: BS: House insulation question
From: Grab
Date: 14 Nov 05 - 08:07 AM

Rome: Possibly increased damp, due to moisture not being able to evaporate from inside the cavity wall.

Subject: RE: BS: House insulation question
From: JohnInKansas
Date: 14 Nov 05 - 03:23 PM

Rome:

Some air exchange is needed to keep the house from getting "dank." The amount needed will vary a lot with climate and season, and with the "damp load" from people, animals, and cooking. Generally adding insulation only blocks small air leaks, so it shouldn't normally have a significant effect on the amount of "intentional ventillating" needed. Ventillating can usually be seasonal, unless a specific problem pops up.

The increasing use of tightly sealed (and heavily insulated) houses has resulted in mandatory "Radon testing" in the US to qualify for Federally insured mortgages. Nearly all minerals emit small amounts of Radon gas, which is "radioactive." In very tightly closed spaces it can accumulate. Minimal amounts of ventilation at fairly regular intervals, perhaps just annually, will prevent accumulation of what is generally considered hazardous, since the emission is usually very low-level and slow. Usually normal traffic will maintain "safe" levels in main living areas, but accumulation of fairly high levels sometimes happens in basements and in rooms that are closed off for long periods. This is not specifically an "insulation" effect, but extreme efforts to block off all the air leaks could contribute to some accumulation.

Radon accumulation problems usually occur with "all electric" newer homes that are (improperly) built from scratch to have extremely low "leakage" and without provision for air exchange. Adding insulation to an existing home, and especially to an older one, isn't likely to make things that tight.

Some "add-on" insulating materials do emit (outgas) rather rude components, especially for a short time after installation. Depending on the products used, you may find it advisable to ventilate thoroughly for a few days, or for a couple of hours a few days apart, immediately after the installation, although with other common products this may not be necessary. If in doubt, ask the installer(s).

John

Subject: RE: BS: House insulation question
From: danensis
Date: 14 Nov 05 - 03:59 PM

Before going in for any form of cavity wall insulation I would take a look at Jeff Howell's comments:
http://www.ask-jeff.co.uk/building-cavity-wall-insulation.htm

Subject: RE: BS: House insulation question
From: GUEST,Rome
Date: 15 Nov 05 - 01:41 PM

Thank you to all the people who replied to my question. The surveyor is calling tomorrow. With your replies I shall be able to ask the right questions!

Subject: RE: BS: House insulation question
From: gnu
Date: 15 Nov 05 - 04:08 PM

I used to find a lot of good info at http://www.inspect-ny.com, www.carsondunlop.com, www.ashi.com, and best of all, www.cmhc.ca

Subject: RE: BS: House insulation question
From: GUEST,Rome
Date: 18 Nov 05 - 01:33 PM

Having read the "Ask Jeff" site comments, I cancelled the surveyor and decided not to go ahead with the insualtion on the grounds of "if a thing is not broken don't try to mend it!" Thanks for your help.

Subject: Chimney brick question
From: GUEST
Date: 06 Dec 05 - 09:11 AM

My chimney (cement blocks) is wet in the attic. The attic is well ventelated (ridge vents and soffit vents. I reflashed the chimney twice and it is still wet. I think what is happening is that water is condensing on the ice-water barrier below the flashing and then dripping down the chimney. I cant ventilate the attic any more. Is it possible that ice/water barrier is too airtight and some air needs to escape through the chimney flashing? This is driving me nuts.
-kevin

Subject: RE: BS: House insulation question
From: MMario
Date: 06 Dec 05 - 09:27 AM

It could be that the brick is conducting heat and the moisture is condensation from the air. You may need a de-humidifier. Or you may need a better air circulation from the living area into your attic.

Subject: RE: BS: House insulation question
From: Barry Finn
Date: 06 Dec 05 - 12:41 PM

A block chimney is very porous & should be protected with a paint or a top coat of some kind so it won't suck in the moisture.


You may also want to check the chimney (if it's brick or block) that first, the counter flashing which is the top flashing that should be imbedded into a raglet that's cut into the mortar maybe 8"-12" above the roofing (more difficult on block than on brick). Make sure the step flashings on the sides going up the chimney are installed in a proper step fashion & under the counter flashing. The base flashing should also follow this fashion, higher always overlaping the lower pieces. You may have to caulk or re-motar the raglet where the metal should be imbedded into the chimney as well as all the motar joints. Another thing to check would be the chimney cap for cracks. A lot of times you see chimneys sealed with roof cement & the tar covers the faulty flashings a quick fix is to just tar any suspious cracks or gaps with tar & a tarred fiberglass mesh (optional). This will last a few years if done right but it's not the proper method. If the chimney sits in such a way that the high side can't shed water around to the sides of the chimney then you may have a base flashing that's not wide enough & may have to reflash or have to build a cricket behind the chimney (sort of a small roof gable).

Good Luck, Barry

Subject: RE: BS: House insulation question
From: Kaleea
Date: 06 Dec 05 - 12:52 PM

or just plug it up with santa

Subject: RE: BS: House insulation question
From: Donuel
Date: 06 Dec 05 - 03:11 PM

My girlfriend's chimney is also always wet

Subject: RE: BS: House insulation question
From: The Fooles Troupe
Date: 07 Dec 05 - 12:14 AM

Oooooooooooooooooooooooooooooo!

So why don't you help her get her fire lit, you lazy boy?

Subject: RE: BS: House insulation question
From: gnu
Date: 07 Dec 05 - 06:23 AM

Re : From: GUEST , Date: 06 Dec 05 - 09:11 AM

Some questions are in order (you may or may not be able to answer some)......

Please describe "wet" - stained, discoloured, damp, running, ?

Please describe where wet - all sides? full length of attic?

Does the "wet" vary with temperature and humidity? season? rain and wind intensity and direction?

Where "wet", any white stains? any white, crystal-like stuff?

What are the dimensions? Length and width (not height).

Is the chimney moistured-sealed above the roof - painted or otherwise?

Is there a clay or steel liner in the chimney?

Is there a rain cap at the top of the chimney?


Put a hose to it while someone inspects the wet area. Tip... go real sloooooowww.

Subject: RE: BS: House insulation question
From: Bobert
Date: 07 Dec 05 - 07:39 AM

Ahhhh, as fir the chimney being wet, Donuel, yer gonna need to use silicone on it... You can get it in gallons pails and is best applies with one of them cheapie pump spryers like you'd spray plants with... Don't get it on the roof, however 'cause it is slick as owl poop... It will keep the water off ther chimney fir about 5 years before having to do it again... Okay, I knew you were going to ask... Yes you can brush it on, as well...

Ahhh, not only do you have the attic vents which need to stay open but, if your house has a crwl space, it is vented as well and they need to be kept open as well...

Boberr

Subject: RE: BS: House insulation question
From: Skivee
Date: 07 Dec 05 - 11:04 PM

Hey, Bobert,
   Is a "crwl space" where a Welsh fiddle relative is kept, or where rendered terror suspects are detained?
Just wondering.