Negative House Pressure

[energy_rater_La]

good stuff hearthman, I was thinking about you when I wrote my post!
what is that material you use on walls of fireplace..looks like radiant barrier??

[hearthman]

Deb I think we're on the same page with the weatherization schedule. I see they have a foil-backed vapor barrier used over the poured concrete walls in the basement, which is quite common in this region. This house is about 90 minutes south of me, west of Baltimore. It doesn't do much good when the perimeter isn't sealed but it looks cool.

I don't really use any sort of radiant barrier per se around factory built fireplaces since their listing allows clearance to ordinary construction. My main thing is to use products that block air infil/ exfil that have a reasonably low fire spread and are not good food for mold and do not disintegrate as soon as they get wet. That's why I love T-ply and hate drywall in dogsheds and chases. Some installers will sit the unit on a piece of Homosote board as a thermal energy break to the subfloor but that's really only a major problem with concrete floors. Doesn't hurt on frame construction but you do have to make that 1/2" adjustment to your facing materials.

Dirty insulation= air flow. The mixed bag of fiberglass batts in those joist bays are essentially cosmetic and do almost nothing to insulate. Remember, unless insulation is encapsulated on all 6 sides it does not meet its stated R-valve by a long shot.

[energy_rater_La]

thermo ply? I remember seeing pics of it from your postings.

"I see they have a foil-backed vapor barrier used over the poured concrete walls in the basement, which is quite common in this region."
interesting...does it actually do anything as far as radiant heat, or is it the vapor barrier properties
that it is used for?

I see this cantilevered situation often..the things you notice when you drive around..LOL!
most common in new construction is at porches & balconies, cuz we don't have basements
here.

yeah..basic weatherization would have benefitted this builder, but at least
homeowner on on the right track now.

[hearthman]

I guess some salesman told the builder this foil-backed insulation is better than just Kraft paper. It also picks up spills faster than Bounty and slices fruit not to mention trims inches off your waist! This is almost like saying I have insulation in my home--I have a big pile of it lying on my living room floor but I'm still cold. Mis-application of technology or incomplete application. About like using Tyvek without the tape on the seams.

yeaaaaahhh man, Thermo-Ply and Thermo-Sheath. Cool stuff. I use it as fireblocking, draft stopping, protecting floors from work, and of course, my favorite chase wall sheathing material. If you have a chase/ dogshed less than 8ft. tall, you can wrap the inside like a Jiffy Pop with two sheets with one seam horizontally. You measure and cut for two horizontal sheets and bend the sides at 90* but don't cut them into separate pieces. You should have a sheet with three sides that can slip into the chase like a glove. Nail it to the framing with roofing nails or roofing caps. Seal the central horizontal seam with Iron Grip UL 181 tape and pookie the perimeter joints to the framing and subfloor with duct mastic--Done and tight as a duck's rear end. T-ply is thin so I can usually use it without encroaching in my clearance to combustibles the way 1/2" drywall can. If a AHJ forces you to line a chase with drywall, beg them to allow you to use MR board. There is no need for type 'X' fire resistance board unless you are in a commercial application such as a "shaft"---not a chase as in over 4 stories where the full building code then requires fire rated construction. T-ply is fast, light, easy to work with once you've had a little practice and meets all my criteria. There are typically 4 grades in strength but the lowest is fine for weatherization work.

I am looking for a small unit spray foam applicator but most I see that call themselves "spray" and just glorified can foam in jugs with a funky applicator nozzle. I want to batter walls and joints and not just filling voids. Any suggestions? TIA

[taverty]

Thanks for all the feedback. hearthman, you're correct, that foil backed insulation is what's wrapping my concrete foundation. It's in pretty much all the houses around here from the mid 90's on. I have to reattach it in some areas, it's fallen down due to me resting things against it.

I'll call FireSide to have them look at my fireplace chase. I've already had a fireplace shop out (located in Rockville MD) and they said not to do anything with the chase. The guy said I needed to maintain clearances and I can't add any insulation because it would cause the chase to overheat. Then he said I needed to bring in air elsewhere to keep the fireplace from being drafty. They were out right before I had the ventilation system installed. Basically the guy agreed with my energy audit company and said my house was too tight. It did seem like he had a point though. When he opened the window next to the fireplace the draft from the fireplace stopped. After I installed the ventilation system and pretty much nothing changed with the fireplace draft is one of the main reasons I posted here.

This is why I've been all over the place! And also why I really appreciate all of your help!



The bump out in the kitchen does have insulation in the walls. I checked it by opening the electrical outlets and pulling out the dishwasher and making a small hole in the drywall. So I'm not 100% why it's so drafty. I think since the cantilever is just like the fireplace cantilever, fiberglass batts shoved between the joists that's the main problem. The energy audit company did identify a draft up each corner where the plywood butted up against each other. She suggested I spray foam under the gap between the corner vinyl j-channel and the plywood.

So it sounds like the best course of action is to:
1. Have the upstairs attic unit duct blasted.
2. Seal unit upstairs accordingly
3. Have the fireplace chase opened from the outside and properly insulated with Thermo-ply and Thermo-Sheath.
.... How do you completely seal it when you're doing it all from the outside. There is no access now from the inside.
4. Spray foam/rigid foam the cantilever for both the fireplace and kitchen bump out.
... So should I use rigid foam on the bottom of the bump out instead of plywood like there is now? Or more likely: rigid foam then the plywood? Except that means the bottom may stick out too far.

Does this all sound right?

Thanks again!

[taverty]

Just made an appointment for duct blasting. Tomorrow at 2pm. Got the name of the company off of the http://www.resnet.us/ site.

Thanks again. Hopefully they find something!

[hearthman]

When you open a window, you are changing the Path of Least Resistance. Since the rest of the house is like Tupperware, the leaks at the fireplace and bay window were the only substantial leaks left. The air needs to come in regardless so its just a question of whether or not you're going to control where it infiltrates and how much or is nature. It's T-ply or T-Sheath-not both. Foam/ caulk/ seal then insulate, then interior sheathing with the T-ply/ T-Sheath in lieu of drywall.

As for weatherizing from the outside, it helps to do like Steve Martin and "get small". Otherwise, it's a fun day. I typically cut a large access in the outer sheathing big enough for me to crawl in like a window. I vacuum/ wipe down the unit with citrus solvent. Then foam/ caulk/ seal joints and gaps. Next, insulation. I prefer Roxul mineral fiber insulation, not for any fire rating but I think its a lot easier to handle and keep my full loft and fill the bays with it. It's great chinking the cutout for the gas line wherever it enters the chase. Use a serrated bread knife to trim it. Then T-ply with UL 181 butyl-backed tape over the seams or mastic. To seal the "window", I cut some T-ply about 1" bigger than the footprint of the window and bend tabs in so it resembles to lid of a shoe box. Run two straps across the inside face of the framing as a backer. I shove this into the stud bay so the T-ply is essentially flush with the rest of the chase liner then nail the tabs to the framing. The straps help keep the "lid" from going in too far or falling into the chase. Once in place and secured, I pookie the joints with mastic, insulate, replace plywood/ OSB sheathing and caulk the seams where I cut it out. Replace the house wrap using approved tape, then replace the siding and pat yourself on the back. When done celebrating, tackle the cantilever or you can do it concurrently. I block off the joist bays over the foundation wall with T-ply, duct board or rigid foam board and pookie all joints with mastic. Again, pookie all the seams from below, insulate then sheath. You really should use a CDX plywood underneath. This is an area prone to condensation and rot. If you use OSB or even my beloved T-ply, it may soften and allow rodents to enter. Some builders will cover the undersize with either vinyl siding or aluminum coilstock. I reccomend against the impervious sheet aluminum. You want this area to breathe and dry out. Plastic siding is a suitable inexpensive alternative. When you go to install the plywood against the underside, you run beads of latex caulk around the perimeter for a removable airtight seal. Don't use silicone caulk. You want to be able to remove that plywood in the future God forbid.

As for the driving force of your depressurization, what about upper level leaks? We discussed the duct work but what about the attic penetrations? Attic stairs/ hatch, recessed lights, mechanical chases, speakers, bathroom fans, etc.?

[stvc]

I've been following this thread for a bit but haven't replied because I just didn't have enough time to type everything I wanted to say. At this point most of it has been covered but just wanted to stress that for all that infiltration at the lower levels there has to be ex-filtration at a higher level. I suspect the duct blaster is going to identify that.

One more thought is the roofs of those bump-outs. I've seen problems there, the wall sheathing not continuous with soffit vents basically venting through the wall.

All in all sound like you are on the right track and look forward to hearing how it works out. We can all learn here and especially liked hearthmans approach to the fireplace chase. I would like to see him doing that!

[tipsrfine]

I've been following this thread from the start. Lots of really good thoughts from everyone. The OP has indicated the major "air in" spots, but I have not heard any good ideas on the "air out" spots. The "air in" seems to occur regardless of whether or not the HVAC air handler is on, and I don't see stack effect causing so much "air in". My intuition is for wind driven air infiltration/exfiltration. Some homes are just in wind tunnels, caused by terrain and the homes that surround them. I've had one homeowner who has her bar-b-que grill blown all across her yard with the propane tank still attached because of this wind.
A simple smoke pencil should determine where the "air out" is, since we know where the "air in" spots are. Infrared would work also. The use of a manometer for pressure differences between rooms/hallways/attic/basement would be useful also.
Air in = Air out, and visa versa.
The answer is there, it's just hidden; that's what testing equipment is for. Even a piece of tissue paper can be a testing instrument. Walk around with one and hold it near windows, light fixtures, bathroom exhaust vents etc..., and see if it blows out or in. Air in = Air out.

[taverty]

tipsrfine, I heard the same thing about air in must equal air out. That's why I was really trying to focus on the upstairs before tackling the bump outs. It stinks because those two bump outs are in the two most heavily used rooms (family room/kitchen) making them really drafty and uncomfortable.

I thought driven wind as well at some point but we're fairly well protected by trees and other houses. My friends neighborhood a few minutes away sits up high and the houses there are always loosing siding and roof shingles. When sitting on his deck you'd get big gusts throwing paper plates and cups of beer :-). Unless there's a storm coming we've never had issues with strong winds.

I agree, I think the issue is just hidden, but damn it, I'd like to find it! I'm really hoping the duct blasting today will give me that smoking gun. If it doesn't, I'm not even sure what to try next!

hearthman, almost all of the ceiling penetrations that were identified on the audit report were sealed with caulk and expanding foam. The bath fans (they were really bad!), recessed light (only one), attic hatch, almost all electrical boxes, almost all plumbing penetrations and a mechanical chase were all sealed up. The only item left was the top plates, I tried to seal some of them, but it was just too difficult.

The worst part, it felt like sealing those items didn't make a bit of difference. I know using my hand isn't scientific or accurate, but that breeze felt pretty much the same the night after I did the sealing.

I've somewhat verified the ceiling penetrations by walking around with my black and decker temperature gun. The bath fans, recessed light and attic hatch are now at the same temperature as the ceiling around it.

Thanks, and I'll post back with what the duct blasting company finds.

[energy_rater_La]

looking forward to duct testing results.
make sure that return leakage is seperated from supply leakage.

what to expect..in case you don't know.
each supply grill will be covered, return will be covered with duct
blaster & sealed off air tight also.
then ducts will be depressurized to 25 pascals.
this will give you the amount of leakage.

what I like to do, is once the leakage #'s have been recorded,
to reverse the air flow of the fan. going from depressurizing,
to pressurzing the duct/return system.
then go into the attic with a roll of tape to mark leakage sites.

supply take offs on plenums, plenum to equipent connections,
return to return framing & framing to framing members & attic floor
should all be felt around for air leakage.

the duct blaster isn't measuring now...its just blowing, don't expect
the readings to tell you anything. you are simply finding the leaks.
you want to be in the attic, verifying & marking the leakage sites.
then address as in my garden web post.

ask the tech to do this. if they haven't done this before...its a
real eye opener. instead of just #'s you know where it leaks.
to me the whole equiv leakage area doesn't mean much if you don't
know where the leaks are.

as you seal your high leaks & low leaks your mechanical ventilation
system will provide the air changes per hour as needed.

hearthman & I seem to be on the same page as to opening the
bumpouts & sealing them. this is basic weatherization, done right.
sometimes it is close quarters, but if you have the want to do it, and
a plan...it works out well.
you'd be amazed at how much you can do by cutting a 2'x3' hole in the wall.

having spent many a day inside return air chases...you learn it helps to
have someone 'outside' to hand you sheathing materials.

best of luck.

[taverty]

energy_rater_la, thanks for the information! I wasn't 100% sure what a duct blasting entailed. I will definitely ask them to run the test in reverse to locate the leaks. Again, I'm so appreciative of the help, I wouldn't have even thought to ask them about this!

[energy_rater_La]

the things you learn when you play around with your blower door! LOL!

[hearthman]

to add to energy _rater_La's position,

Nothing is as convincing as seeing the leaks. Numbers are cool but seeing stuff blowing in the breeze really drive home the issue. Wherever you see insulation being blown away during the pressurization test, just see dollar bills and comfort blowing out of the house. Now, which are you going to focus on: the small leaks that are within easy access or the open barn doors that invariably seem to be more difficult to get to? Plan on making reliable access including 3/4" plywood catwalks screwed into the tops of joists so they don't flip and dump you through the ceiling or hurt you. Do what you gotta do to clear away the cotton candy to get at the work area to do it right. Once it's all sealed, fire up the fan and check it from the attic again before covering up with insulation. Here's where a smoke source can be very illustrative. What leaks under pressure may not leak under vacuum and vice-verse hence test both ways. While TiCl4 is the best stuff I've ever used to show minute air movements, you can get an inexpensive smoke puffer on the web that uses model railroad locomotive smoke generator fluid so its safer.

Remember to check over all the interior walls looking for air bypasses and missing top plates as these can be huge losses. Plumbing and electrical penetrations into the attic along with combustion venting rank pretty high, too. For those wanting to seal around chimneys and vents, be careful. The code requires stated clearances to combustibles on masonry chimneys with sheetmetal firestopping that can be caulked to a masonry chimney but all factory built chimneys and vents can only be caulked if their listed instructions allow it. Some systems, esp. air cooled woodburning fireplace chimneys can NOT be caulked at firestops and to do so may actually cause the chase to overheat and could lead to fire.

Having that Duct Blaster is a golden opportunity so take full advantage. Who knows, you may locate disconnected ducts you never could otherwise even when the blower door numbers showed a leak "somewhere".

Side note: back to my fireplace chase: there should be "fireblocking" above the fireplace at the ceiling level per the code. This can be any number of materials listed in the 2009 IRC R302.11 or otherwise approved by your AHJ. For me, either 3/4" plywood or 26 ga. galv. sheetmetal are the more common materials for overhead but T-ply can be used if approved by the AHJ. It just has to provide "an effective barrier" to slow fire' spread and contain much of the smoke. Since the area above a fireplace in a dogshed is technically an "attic", treat it as such. This means air sealing and insulation but being so small, these areas seldom require ventilation. I've never seen ill effects from not ventilating these micro-attics but I have seen cold air issues from ventilating them. I've never seen shingle failures from non-ventilated dogshed attics. If you're really worried about venting this area, you may consider something such as this: http://www.roof-2-wall.com/

One last note on attics and HVAC equipment: The code prescribes minimum access size, which most attic pull down stairs barely meet but many of these stairs are not rated for the load of one man, let alone carrying heavy equipment. Before using wooden stairs, take a wrench and tighten the truss rods and bolts so you don't take a nasty spill. There must be a solid stable landing place where you enter the attic. When equipment is located up there, there must be a light switch located within reach of the stairs and there must be a grounded 125 vac outlet within 25 feet of the equipment. There must be solid catwalks 24" wide and the equipment must be within 25 ft unobstructed walkway unless the catwalks are 30" wide and adequate lighting along the way. Don't forget safety. How are you going to rescue a worker disabled when he's wedged in the attic out near the eave in a low pitched roof with 2x4 trusses and no catwalks out to him?

We can talk about weatherizing pull down stairs vs. replacement choices later. Fun stuff!

[energy_rater_La]

@ hearthman too bad we can't do a project together...it would be so much fun!

[taverty]

Ugh!!! 108CFM@50Pa Great! But not the smoking gun I was looking for. He said their company has sealed system's to get to numbers like mine. I was up in the attic with the rep and we were feeling collars, almost nothing was leaking from the collars. One or two you could feel, but barely! No moving fiberglass, nothing!

The company was great, the guy was really nice and tried to look for anything else obvious. He couldn't see anything that stood out. He had some decent suggestions, try keeping the basement door open to move the pressure plane down. But other than that I'm really at a loss now.

I'm going to go back into the attic this weekend to look for more black fiberglass... It has to be there!

Thanks again.

[hearthman]

Ugh!!! 108CFM@50Pa Great! But not the smoking gun I was looking for. He said their company has sealed system's to get to numbers like mine. I was up in the attic with the rep and we were feeling collars, almost nothing was leaking from the collars. One or two you could feel, but barely! No moving fiberglass, nothing!

The company was great, the guy was really nice and tried to look for anything else obvious. He couldn't see anything that stood out. He had some decent suggestions, try keeping the basement door open to move the pressure plane down. But other than that I'm really at a loss now.

I'm going to go back into the attic this weekend to look for more black fiberglass... It has to be there!

Thanks again.

Was that at 50 Pa or 25 for the Duct Blaster test? Also, confirm this is 4,523 square feet of conditioned space? Been reading back through but did you do a Subtraction Method to calculate leakage to the outdoors on the duct system? Did they have a fog machine or IR camera?

[tipsrfine]

Taverty, in your #17 post you mentioned noticing air coming from your downdraft vent when the wind had started to pick up. You also made mention that you noticed drafts blowing through the electrical sockets in the outside walls; where are those electrical sockets located? First, second floor? Does it blow through sockets located on all the outside walls, or just one side of the house?
Was that a bathroom exhaust vent I saw in the video? Did you check that for draft? Lastly, what is that, looks like pvc pipe, in the attic video-you can see it at the 5:09 mark in the video. Looks like it has some kind of orb shaped thing in the middle of it.

[taverty]

hearthman, 50Pa is what the tech said. I knew it was trouble when the display read "LO" and he kept having to add collars to the fan. He didn't have a fog machine or IR Camera and he didn't seem to be calculating anything. What is the subtraction method?


tipsrfine, when the wind picks up, we definitely get more air coming through the downdraft and fireplace. But even on a dead calm cold night there is a steady stream of air coming in. The really drafty electrical sockets are on the back and left side of the house on the first floor. The absolute worst one is on the wall to the right of the kitchen bump out. Even the outlets in the bump out aren't as drafty as this outlet. It's interesting the outlets on the front of the house have no perceivable draft, right ride ever so slight. Rear and left side, you can feel it.

I haven't fully checked my bathroom exhaust vents. Before I sealed them with caulk and foam I only checked to make sure the little plastic backdraft damper was opening and closing correctly. I'll double check for any leakage this evening.

That PVC pipe is my radon pipe, the orb is my radon fan. I had a slightly elevated Radon level and that fan runs 24/7 to depressurize under my basement slab so the radon goes out that pipe instead of into my living space.

Thanks again!

[stvc]

Well, this is a challenging one.

You've done everything right and got all the data needed that should produce some answers but back to square one.

All the symptoms and high bills all lead to a house that leaks like crazy but the blower door-test says otherwise. I can't help but wonder if the gauge may not have been set right or something was wrong with that test. Were all the doors in the house [interior] open? Basement included in conditioned space and Volume? Were you able to walk around and observe leaky areas during the test?

I'm really guessing here but the facts just don't add up. If you haven't already I would suggest a follow up call with the original auditor to update them on the situation. If it were me I would want to know what was going on and run another test. I suspect they may plus it would be helpful to see what if any changes have occurred after improvements.