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Stephen Tashiro
11-25-2018, 6:05 PM
Is it best practice to seal the gap between where drywall meets the top plate of a framed wall as the drywall is installed?

In this video, the insulation contractor must seal this gap while working in the attic. https://www.youtube.com/watch?v=fB6CbJsb1FM (at 13:30 in the video). Apparently this was done for a house built in the 1950's.

Steve Rozmiarek
11-25-2018, 6:53 PM
Wow, someone is paying them to "fix" that????

It's a non issue of the highest magnitude. See the cellulose insulation on top? no "wall air" is drafting through that. Further, if the wall has air moving in it, you have a bigger problem somewhere else.

Charlie Velasquez
11-25-2018, 7:18 PM
I don't know of any rockers that seal interior gaps. They tape the joints of the wall and ceilings, but the air flow in the video is from the air leakage into the wall cavity, then out into the attic, which would be behind the taped ceiling joint.

I think, as the video suggests, it is probably easier and more efficient if the insulation sub guys do it when they insulate.

Paul F Franklin
11-25-2018, 7:20 PM
Best practice these days is to spend more time and effort and budget air sealing rather than just dumping in more insulation. Air will definitely move through cellulose insulation, as well as fiberglass, and rock wool. Pretty much everything other than closed cell spray foam, and even that often develops air leaks when it shrinks a bit and pulls away from the framing members. Building scientists now understand that insulation itself does very little to impede air flow (and moisture). If you want to learn more....I recommend the green building advisor web site.

Steve Rozmiarek
11-25-2018, 7:39 PM
Best practice these days is to spend more time and effort and budget air sealing rather than just dumping in more insulation. Air will definitely move through cellulose insulation, as well as fiberglass, and rock wool. Pretty much everything other than closed cell spray foam, and even that often develops air leaks when it shrinks a bit and pulls away from the framing members. Building scientists now understand that insulation itself does very little to impede air flow (and moisture). If you want to learn more....I recommend the green building advisor web site.

Wait, it's an interior wall, explain where the moving air is coming from??? This is a fantastic example of book smart vs real world. Spend the $ someplace it really matters, like doors, windows, HVAC, etc. If you have enough $ to worry about this "air leakage", I want you as a customer, and I'd be happy to devise a solution. It won't be cheap, but it's for the greater good, so I'm sure you won't mind paying dearly to properly stop that .1 cfm of leaking air. The cost/benefit payoff on "fixing" this is probably 300 years to breakeven, but your great x 5 grandchildren will appreciate the effort.

Nevermind that the exterior door lets out the equivalent of a year's worth of this leakage each time it opens. Really the only solution is for people to forgo HVAC altogether, then it won't matter. Shish.

Lee Schierer
11-25-2018, 7:49 PM
It would easier to use spray foam and seal the leaks with the foam insulation.

Doug Garson
11-25-2018, 8:02 PM
Wait, it's an interior wall, explain where the moving air is coming from??? This is a fantastic example of book smart vs real world. Spend the $ someplace it really matters, like doors, windows, HVAC, etc. If you have enough $ to worry about this "air leakage", I want you as a customer, and I'd be happy to devise a solution. It won't be cheap, but it's for the greater good, so I'm sure you won't mind paying dearly to properly stop that .1 cfm of leaking air. The cost/benefit payoff on "fixing" this is probably 300 years to breakeven, but your great x 5 grandchildren will appreciate the effort.

Nevermind that the exterior door lets out the equivalent of a year's worth of this leakage each time it opens. Really the only solution is for people to forgo HVAC altogether, then it won't matter. Shish.
Where did you get the .1 cfm of air leakage from? The video indicates they reduced leakage by 335 cfm or 20%.

Stephen Tashiro
11-25-2018, 9:21 PM
Wait, it's an interior wall, explain where the moving air is coming from??? .

Interior walls have electric receptacles and their baseboards usually don't make a good seal. So air can flow through them. The point of sealing the attic is to keep air from inside the house from going up into the attic. The video would be more scientifically informative if the air flow readings were taken at various stages during the project - with old insulation in place, with it removed, with some areas sealed, with all the sealing done.

Steve Rozmiarek
11-25-2018, 10:58 PM
Where did you get the .1 cfm of air leakage from? The video indicates they reduced leakage by 335 cfm or 20%.

It's a pure guess based on what I see at work. I'm a carpenter, I'm familiar with this subject, so a somewhat educated guess I guess. The average house that I see has several leaking bathroom vent fans, a dryer vent that is clogged partially open and leaking air, at least one window that doesn't latch correctly, not to mention several windows and probably a door or two that leak around the frame. Any two of those things could allow 335cfm of air movement, I'd be shocked if they couldn't get it reduced that much. They said it was a 1950's bungalow so they picked an easy target.

How's the air quality in a sealed tight house?

Steve Rozmiarek
11-25-2018, 11:14 PM
Ok, but for that to happen the house has to be at a vacuum or under pressure. If it's under vacuum, things like chimneys on non direct vent water heaters and furnaces fail. In my house, a 1918 bungalow, if I leave a bathroom vent fan on for a few hours, the carbon monoxide detector will go off in the basement by the water heater because it's backdrafting. I've see a restaurant hood literally suck the fire out of a water heater from backdrafting force, and it was moving about 400cfm.

Point is, air tight does not automatically equal better. There are a lot of expensive things to get right before worrying about that little bit of air leaking around an interior wall plugin under vacuum. In my day job as a carpenter, I've never seen even one house that has everything so perfect that they would benefit from sealing that plate to drywall seam. In the real world, there are plenty of other things to spend the money on.

Keep in mind, you screw off the sheet of drywall to that top plate, so unless the crew who put it up wants call backs because the seams are cracking, it's tight. If it wasn't, the seam would crack and someone would be fixing it.

Bill Dufour
11-25-2018, 11:15 PM
My house built in 1949 has many air leaks into the walls through the base plate. To run pipes up from the crawl space and electrical down from the attic they did not drill holes. They may have drilled holes then they chopped them bigger with hammer and chisel. Plenty of air space around each penetration top and bottom. I could watch dust float upwards when I had some walls open. Of course any fireblocks do not form a airtight seal just close enough.
Bil lD.

Doug Garson
11-25-2018, 11:31 PM
It's a pure guess based on what I see at work. I'm a carpenter, I'm familiar with this subject, so a somewhat educated guess I guess. The average house that I see has several leaking bathroom vent fans, a dryer vent that is clogged partially open and leaking air, at least one window that doesn't latch correctly, not to mention several windows and probably a door or two that leak around the frame. Any two of those things could allow 335cfm of air movement, I'd be shocked if they couldn't get it reduced that much. They said it was a 1950's bungalow so they picked an easy target.

How's the air quality in a sealed tight house?
So it looks like your educated guess was off by about 334.9 cfm based on the actual measurements made in the video. Don't disagree that you could save an additional 335 cfm or more addressing the things you listed but that's not a reason not to do what they did.

PS I just watched the end of the video again and I misquoted it, the actual number was 335 cfm, still 20%.

Charlie Velasquez
11-26-2018, 4:01 AM
That 335cfm in the video was sealing all the air leaks into the attic; the ones from the wall cavities via the switches, outlets, and possible base trim PLUS the ones from all the electrical, plumbing, hvac penetrations, and the access opening.
I would guess the latter group is the bulk of the air transfer, and most insulation contractors would agree those should have been sealed.

The opening poster's inquiry was that 1/16" (nickel thickness- which would probably be on the big side) gap along the top plate of mostly interior walls.

Those top plate gaps may have been cost effective to seal during initial insulation, but if the other penetrations were sealed when insulated, I don't think it would be cost effective to remove and dispose of prior insulation to remediate the top plate.

Edit: so the op is really asking if it makes sense for the rockers to shoot a thin bead of caulk or glue along the edge of the top plate prior to hanging the wall sheetrock.

John Goodin
11-26-2018, 9:53 AM
The flip side is that some major home builders are putting fresh air intake fans in their homes. They say modern homes are so tight they have to mechanically bring in fresh air.

Tim Bueler
11-26-2018, 11:34 AM
Best practice these days is to spend more time and effort and budget air sealing rather than just dumping in more insulation. Air will definitely move through cellulose insulation, as well as fiberglass, and rock wool. Pretty much everything other than closed cell spray foam, and even that often develops air leaks when it shrinks a bit and pulls away from the framing members. Building scientists now understand that insulation itself does very little to impede air flow (and moisture). If you want to learn more....I recommend the green building advisor web site.

I didn't watch the video but +1 on what Paul says. I'm a 30+ yr custom home builder/remodeler and I follow the energy conservation movement extensively. Early attempts at air sealing, such as the Super Good Cents Program (mid 1980's?), were a disaster. Fortunately building science has come up with some fantastic solutions.

Proper air sealing can mean the difference between heating your home with a 4 or 5 ton heat pump, with full duct work system, vs. heating with 2 ton worth of mini-split. The cost savings on energy efficiency is like compounding interest. Yes, air quality can suffer. Fortunately we now have Heat Recovery and Energy Recovery Ventilators available. These can easily be bought and installed with the savings from a mondo jumbo heating system. Some are running up to 85% efficiency. The basis is they pre-heat and/or cool air entering your home whether by bath fans, kitchen fans or just the need/desire for fresh air.

Many of the top (quality, not volume) builders today feel air sealing is so important they are actually not framing interior walls until the drywall is hung and fire taped on the exterior walls. Yes, it requires more effort, pre-planning and forward thinking but it is the future IMO. From what I'm reading in my journals extra expense for super energy efficiency is running an extra 10%-15% on the cost of building of home. But energy savings are so great payback on investment is getting down to around 5 yrs or so. After that any savings are essentially money in your pocket. This effort also contributes to occupant comfort by eliminating cold spots and drafts (like the house I grew up in, brrrr).

Steve Rozmiarek
11-27-2018, 2:08 AM
I didn't watch the video but +1 on what Paul says. I'm a 30+ yr custom home builder/remodeler and I follow the energy conservation movement extensively. Early attempts at air sealing, such as the Super Good Cents Program (mid 1980's?), were a disaster. Fortunately building science has come up with some fantastic solutions.

Proper air sealing can mean the difference between heating your home with a 4 or 5 ton heat pump, with full duct work system, vs. heating with 2 ton worth of mini-split. The cost savings on energy efficiency is like compounding interest. Yes, air quality can suffer. Fortunately we now have Heat Recovery and Energy Recovery Ventilators available. These can easily be bought and installed with the savings from a mondo jumbo heating system. Some are running up to 85% efficiency. The basis is they pre-heat and/or cool air entering your home whether by bath fans, kitchen fans or just the need/desire for fresh air.

Many of the top (quality, not volume) builders today feel air sealing is so important they are actually not framing interior walls until the drywall is hung and fire taped on the exterior walls. Yes, it requires more effort, pre-planning and forward thinking but it is the future IMO. From what I'm reading in my journals extra expense for super energy efficiency is running an extra 10%-15% on the cost of building of home. But energy savings are so great payback on investment is getting down to around 5 yrs or so. After that any savings are essentially money in your pocket. This effort also contributes to occupant comfort by eliminating cold spots and drafts (like the house I grew up in, brrrr).

My argument that is that 10-15% extra investment in a new home is a poor investment. Retrofitting an old home to these standards is also far more expensive than a new home. In this area, electricity is expensive and gas is cheap, electric heat is about twice the monthly gas bill. Here you can also install a typical gas forced air furnace/ac for far less than a mini split system for a house. The climate here renders any air source heat pump ineffective for a heat source for a large portion of the winter, causing those systems to run on backup heat, usually electric. If all you did with your HVAC system was cool, then you are right, the smaller system is cheaper to operate. Trouble is, a good portion of this country requires heat to, and that changes the equation. For simplicity sake, assume that the small system saves money for half the year while cooling, and the cheaper heat source saves money in the other half, resulting in partial or possibly whole offsetting of running costs between the two. Because the installation cost is significantly less for a boring old high efficiency gas furnace, you are paying more for the heat pump equipment, but maybe not saving anything on the bill.

I agree, a heat exchanger is a great thing. It's however only pre-cooling/warming air that needs changed in a tight house to get rid of stale air. To effectively use a heat exchanger in a make-up system to get to all the possible stale air locations, you'll need air movement. Bathroom vents and stove hoods move some, but what about stale bedrooms or basements? You end up needing a duct system of some sort to make it work correctly again, which adds more cost to an already expensive system.

Question is then, if the cost of heating/cooling is the same between two units, but one costs a lot more to install, and requires 10-15% premium to my house, how is that a good investment? In this area, the typical carrier or lennox system will run around $15,000, the last two whole house mini split systems I priced out were not quite twice that (fairly complex systems). I haven't priced an air source ducted system recently, but the last one (6 years ago) was between the two. I have a ground source (pump and dump) going in right now on a remodel that is same price as the large mini split system when the tax credits are applied. I'm sure those prices are different for others because of vendors, fuel sources, and climate, but they are what I deal with, doing the same job you do.

Given that, when I'm selling a new house here to a rational customer, I don't see how I can successfully pitch spending $50-60k more to make a super efficient house, with a ROI that is much longer than the lifespan of the equipment they are being asked to buy, and in most cases, longer than the new homeowner's expected time on this earth. Dirty little secret is that any way to increase a house price, increases profit margin, so I'm sure this movement will continue as long as that "green" money keeps flowing.

Tim Bueler
11-27-2018, 11:30 AM
Given that, when I'm selling a new house here to a rational customer, I don't see how I can successfully pitch spending $50-60k more to make a super efficient house, with a ROI that is much longer than the lifespan of the equipment they are being asked to buy, and in most cases, longer than the new homeowner's expected time on this earth. Dirty little secret is that any way to increase a house price, increases profit margin, so I'm sure this movement will continue as long as that "green" money keeps flowing.

Nothing wrong with increasing the profit margin. Good business people do it every chance they get. And a customer's rationale is subjective to your own view point.

I can tell by your arguments you're not going to be convinced there may good alternatives to the way things have always been done. Certainly advanced building science isn't for every builder nor every customer. And, yes, in some circumstances there is a poor ROI. For some customers, and I've had many over the years, it's not about the immediate dollars. It may be about lessening the impact, the carbon-footprint if you will. For others it may be about having something out of the ordinary :cool:. Or maybe something innovative. There could be any number of reasons.

I was fortunate enough to have had my career in an area with ample quantities of forward thinking customers. That afforded me the opportunity to advance my skill and knowledge far beyond my first mentor who regularly stated "That's good enough" and "We ain't buildin' a piano". Certainly there is plenty of room still for that type of builder. I suspect there always will be.

I would also agree that it is more difficult to upgrade an existing home, yet we did just that a number of times. Again, for those customers of mine undertaking those improvements it wasn't about the dollars. Of those I can recall it was more about comfort. They wanted to be more comfortable as they planned to age in place. The savings on utility costs were something we'd discuss as a possibility but were invariably a bragging point (on how much less they were paying :cool:) months or years later when I'd run into them somewhere.

I would also agree that there are regional differences of OPINION on what works best. I can promise you there are advanced builders in every state (even Nebraska ;)) building far beyond code and status quo. Frankly, I think recent advances in building science and technology are exciting. Far more sustainable and comfortable than the houses my grand father built 70 or 80 yrs ago. Of course, I'm not driving a Model A like my grandfather did, or a horse and buggy like his dad. The Wright Bros. Kitty Flyer is hardly a 787 jet plane. Change happens, embrace it or not, it's up to you.

Also, on ventilation. When one turns on an exhaustive or combustion devise (bath fan, wood stove, gas furnace), there must be make up air coming from somewhere. There are many, many stories of poor air quality in houses that weren't "sealed too tight". Backdrafting of combustion appliances, make up air coming in laden with mold or ??? from the under crawl (or in the OP's case, the attic), CO gas coming from the garage, etc. Heat/Energy Recovery Ventilators make it possible to not only control exactly where your make up air comes from and goes to, but also filter it in the process. In this case it may be even more important for energy upgrades in an old house as those issues in a newer house may be addressed by building code depending on the local authority. I almost always bumped heads with building code inspectors, but that doesn't mean I don't understand how the codes came to be. Yesterday those issues weren't known and today there are always builders and/or customers wanting to cut corners.

Different strokes for different folks. If the OP wants to try some advanced building techniques I say go for it. I also highly encourage reading all you can for those who are interested. The aforementioned Green Building Adviser is a good reading source that will lead to others. Building Science Corp is another place for those who really like the science. They are, IMO, the premier building science consultants in this country today. A person could spend years reading about this stuff...Oh Wait! I have :D. It's fun and interesting.

Steve Rozmiarek
12-01-2018, 5:40 PM
Also, on ventilation. When one turns on an exhaustive or combustion devise (bath fan, wood stove, gas furnace), there must be make up air coming from somewhere. There are many, many stories of poor air quality in houses that weren't "sealed too tight". Backdrafting of combustion appliances, make up air coming in laden with mold or ??? from the under crawl (or in the OP's case, the attic), CO gas coming from the garage, etc. Heat/Energy Recovery Ventilators make it possible to not only control exactly where your make up air comes from and goes to, but also filter it in the process. In this case it may be even more important for energy upgrades in an old house as those issues in a newer house may be addressed by building code depending on the local authority. I almost always bumped heads with building code inspectors, but that doesn't mean I don't understand how the codes came to be. Yesterday those issues weren't known and today there are always builders and/or customers wanting to cut corners.



Tim, you do have a good point about the make up air source being more directable in a tight house. I'm sure you've seen them to where the filthy old chimney is the main duct for "fresh" air back into the building when a vent fan is on. That's not good for anyone.

I don't know of any builders that are able to completely do it their own way, the customer gets to make most of the choices. I don't believe it's "builders and/or customers wanting to cut corners", but rather people trying to get the most for their hard earned buck. My customers pay me for my experience in the industry, and use it along with whatever else they've gleaned from other sources to make decisions. I'm sure you've been there to when a customer picks the less efficient windows or doors to be able to get a fancier kitchen. In the real world, that's how building happens, and it's why I find the Green Building Advisor or the like, of very little use, unless they come up with a quicker, cheaper or prettier way to do something. I'd be happy to build to those specs if someone wanted them, they just don't here, for very good reasons. In my experience the way it really happens, is a never ending struggle to squeeze every last drop of usefulness out of every penny, and a 40-60 year investment break even has zero chance in that environment.

Tim Bueler
12-02-2018, 10:29 AM
Steve, I think we'll agree to disagree. I've seen way too many corners cut, in fact I've had customers call me in to fix things that shouldn't have needed fixing.

It sounds like you are selling on price. I never did. I sold on features. Yes, they cost more. That's why you have so sell them. If you sell $15/hr work, that's what you'll get. Likewise if you sell $50/hr work. That was the difference between my first mentor and myself. He never could figure out how I could charge so much. My tax return may have said "Home Builder" but my real job was "Salesman". It depends on who you market to. I was very fortunate to live in a region with the likes of Microsoft, Nintendo and Boeing. Then you add on a whole plethora of support industries to go along with those. Many of my added features were an easy sell. Shoot, with all those creative people it was often them coming to me asking "Can you do this?". Then it's all in how you frame your response. Once I had built a reputation on not-the-status-quo they came looking for me. DON'T focus on price or you will loose the sale.

Example: LOML and I were looking to buy a new travel trailer many years ago. Went to a dealership that had some models we liked. They were the higher end models. The salesman showed us through their cheaper models. We weren't interested and asked about the higher end models. I remember his response to this day, "Oh, you can't afford those...they're way too expensive." We ended up buying a top of the line model, but not from that dealership.

The modern "green building" push isn't for everyone, certainly, but I had great success selling exactly the things you say people won't buy. That there are so many people and information dedicated to that says I'm not the only one. Thankfully, the building industry is going through some great changes after a century or so of stagnancy. It's about time. Traditional building practices are outdated and obsolete and long overdue for an update. There will be many more changes. As I said, it's exciting! Have you read about Net Zero? It's achievable! Even some of the big national builders are jumping on the band wagon of super insulation, energy efficiency and energy production. And banks are loaning on it. It's being done! Imagine never having another utility bill as long as you own your home! That's exciting! But you're right, it's not something everyone can (or wants to) afford. But just like high end travel trailers, that doesn't mean they don't exist and it doesn't mean there aren't customers who can afford them.

Ok, stepping off my soap box now. :D

Steve Rozmiarek
12-02-2018, 2:30 PM
Tim, it's interesting the differences in housing regionally. I'd hazard a guess that the median house price in your area is at least double what it is here. There are people that make a very nice living here, but it's a completely different customer base. A kitchen remodel in your area probably costs as much a major remodel and addition does here. It works both ways, cost of living is very low here, so it all works fine. Home prices are directly and heavily impacted by the different states political bias regarding regulation and taxes. Have to feed the beast, so overhead costs are probably much higher in your area too. Kind of the wild west out here still, which is one of the big reasons that people come to this area.

I agree on the salesman aspect, but we just have different customers. There are no corners being cut in my work, my customers just know what they need/want and don't. Most of my customers would actually likely kick me off the site if I tried to sell them green anything because of the area's politics and independence.

I'm casually familiar with the Net Zero concept. We are one generation removed from it out here, so there isn't much desire to go back. Of course there are a lot more amenities to achieve it now, but in this area, people still remember trying to survive the blizzard of whatever with a net zero lifestyle. It wasn't a lifestyle choice back then though, and the comfort of knowing that you have a couple different heat sources is what my customers are buying, not a delicately balanced solution that might fail if the weather gets a little sideways.

Have a good afternoon,