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Thread: Ugg, I am going to have to add cooling

  1. #1
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    Ugg, I am going to have to add cooling

    Summers up here are just getting to be too hot. Think of me as a Newfoundland or sled type dog, just shaped like a human.

    FWIW I am running a Blaze King Ashford 30 in 1200sqft, it was installed May 2014. I cycled 8 cords through that thing every winter for a while, got by on five cords each of the last two winters and might get by with four cords this winter if the weather keeps doing what it has been doing. I do have eight cords ready to go just in case, but it has been uncomfortably hot and humid for me up here this summer for six weeks already, with no end in sight; instead of the usual two weeks of summer misery that should have ended two weeks ago.

    I have two fundamental questions.

    1. Where do I put the vapor barrier in new construction when I am running both heat and AC?

    2. At what square footage or conditioned volume do heat pumps get up on an efficiency plateau? With pellet stoves it is around 1800-2000 sqft. With cord wood stoves some of the smaller ones can do OK now in 1500 sqft, but they also really settle in around 2000 conditioned sqft and up. Typical house size and weather for the lower 48. With these minisplits some of you folks are running it sounds like I could go pretty small for an AC area.

    I am kinda toying with the idea of building the retirement home with attached shop as a cold climate building with the vapor barrier directly under the drywall, heated in the winter with humidity control and fresh air flow in the hot season, and then building a separate but very nearby shed/ tiny house sized building 200-400 sqft with the vapor barrier on the outer face of the wall so I could cool it in the summer as office and sometimes sleeping space, and not go out there in the wintertime.

    3. How do you keep mold out of your insulation when running both heat and AC?

    Thanks for your input, I moved up here to get away from long hot summers and it isn't working.

  2. #2
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    If you have only one, your vapor barrier should be on the interior. It will keep any humidity from exfiltrating and condensing in the wall cavity when it gets towards the cold exterior. In my neck of the woods they put one on the exterior as well, referring to that one as the WRB (water resistant barrier). You want your wall cavity to be like the walls of a thermos bottle with no path for air or moisture transmission in either direction.
    Sharp solves all manner of problems.

  3. #3
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    So many choices these days between foam and fiberglass. I can offer no help but you may want to talk to a insulation contractor to get some pricing and maybe some free advice. All I do know is you want to get this vapor barrier thing right.

  4. #4
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    Air seal and insulate. Don't use plastic insulation, it pollutes in its manufacture, use, and disposal. The propellants used in making foam do so much climate damage that they have to save heat for decades before they lessen climate impact. Cellulose and rock wool pollute less, and can be disposed of easier when they are thrown out.

    Air sealing the conditioned space keeps moist air out of the wall and ceiling cavities. This raises the dew point in the walls, so you won't get condensation. On the exterior, one would normally want to keep water out. Air sealing on the interior reduces chimney effects that pull moisture into the walls.

    Most of all, air sealing the top of the conditioned space keeps the attic dry, and lessens suction in gaps in the building envelope. For example, if you have holes where wires perforate the ceiling, air will chimney out. Pressure is reduced in the living space. The leaky door now becomes a conduit of outside air. That air is warmed and moisturized as it goes through the living space. When it shoot into the attic, it's like a fountain of moisture and heat that creates a biosphere of mold over your head.

  5. #5
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    For cooling, a heat pump split type setup will work for you for mid-spring through mid-fall, but do not expect to be getting heating value from it during the colder times in your geography. Even the best units don't operate with enough efficiency below 0º F to -5º F or stop working altogether as you get close to that,. Stick with your already effective heating setup for that and do a "dedicated to cooling" system for, well...cooling.

    Insulation and sealing done property is important as I'm sure you know. A really well sealed structure will permit you to cool it efficiently with notably lower cost. Do keep in mind that a really well sealed building will need formal ventilation for when you are heating if your wood burning setup is physically inside the structure.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
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    I recommend you spend some time at the green building advisor site. A lot has changed in terms of best practices for air, water, and vapor management and insulation in the last 15-20 years. There are really knowledgeable folks at that site that are welcoming and helpful.
    --I had my patience tested. I'm negative--

  7. #7
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    Scott, the guys at CCHRC at the university are very helpful. I’m also in Fairbanks and heat/cool the whole house with a GSHP. I’m using the “remote” wall system. We can meet up and I’ll show you what I’ve done if your interested.
    Cheers
    Sean

  8. #8
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    Quote Originally Posted by William Hodge View Post
    Air seal and insulate. Don't use plastic insulation, it pollutes in its manufacture, use, and disposal. The propellants used in making foam do so much climate damage that they have to save heat for decades before they lessen climate impact. Cellulose and rock wool pollute less, and can be disposed of easier when they are thrown out.

    Air sealing the conditioned space keeps moist air out of the wall and ceiling cavities. This raises the dew point in the walls, so you won't get condensation. On the exterior, one would normally want to keep water out. Air sealing on the interior reduces chimney effects that pull moisture into the walls.

    Most of all, air sealing the top of the conditioned space keeps the attic dry, and lessens suction in gaps in the building envelope. For example, if you have holes where wires perforate the ceiling, air will chimney out. Pressure is reduced in the living space. The leaky door now becomes a conduit of outside air. That air is warmed and moisturized as it goes through the living space. When it shoot into the attic, it's like a fountain of moisture and heat that creates a biosphere of mold over your head.
    No, spray foam systems use compressed air as a propellant. No, the actual manufacture of part A and part B components of spray foam do not use propellants. No, cellulose is not a great wall insulation because it absorbs water. Yes, walls are susceptible to the chimney effect, but the moisture is coming from outside generally, not inside the conditioned space. The RH outside changes radically throughout a day in most of the north america, as does the temperature. Those differentials in relation to the mostly constant conditioned space temps are what cause condensation. Air sealing exterior walls is for keeping moisture out. Assuming the exterior wall vapor barrier is working, air sealing interior walls is for keeping the cool or warm buy dry wall air from moving in the wall cavity. Ideally you want that air to not move in a wall. No, you are backwards on water damage for attics. The ceiling insulation is generally much thicker than walls (R38 vs R13 as per code), because are incredibly hot and cold, depending on outside and because heat rises, the ceiling becomes the place where insulation is needed most. Generally there is very little air movement within ceiling insulation, which makes cellulose insulation a good product for that zone. The attic space above however, is designed to breath traditionally. Usually air is allowed in through soffits, and out through gable or ridge venting. This use of the chimney effect promotes a healthy, cooler roof, which makes it all last longer. When the attic is turning over air, the moist air coming in the lower vents, needs to exit, so the top vents need constructed as high as possible to allow the warmest, wettest air out. This is why ridge vents are prevalent today.

    Rock wool is not some magical insulation, it is very similar to fibreglass, but costs more and itches less. Ironically, asbestos was the previous generations rock wool. Maybe there is already an attorney working on the next round of lawsuits. I'm not an expert on that though, so take it for the value of free advice.

    Closed cell spray foam insulation has changed the industry. It allows complete air movement sealing within the wall and roof cavities. This function is a great potential tool and can completely change the design of a building. I do not recommend open cell spray foam insulation for anything other than sound deadening.

    I'm a custom home builder and I strongly recommend you be careful who you get this info from. Lots of people have ulterior motives in the "green movement", often not with the homeowner's best interests in mind. I do not know Fairbank's weather, and before I insulated a new home there, I'd make for sure I got intel from someone who works that area that I trusted. Don't rely internet only.

  9. #9
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    Quote Originally Posted by Paul F Franklin View Post
    I recommend you spend some time at the green building advisor site. A lot has changed in terms of best practices for air, water, and vapor management and insulation in the last 15-20 years. There are really knowledgeable folks at that site that are welcoming and helpful.
    I learned so much from them when I air sealed my rim joist and I've seen the results already with reduced AC runtime this summer. Definitely a great place to get the best information on conditioning a building.

  10. #10
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    I will check out green building advisor, thanks for that. Also I will be talking to pros before I break ground, but in general I find folks here know what they are talking about and don't have anything to sell me.

    Sean, thanks for the invite. I will speak to my wife, maybe we can buy you a coffee or something. We are over by Chena Pump/ University West for now. The remote wall system looks good in theory, I am a bit concerned about all those 9 inch screws sagging with time.

    I do appreciate the perspectives on vapor barrier placement. It does make intuitive sense the various ways y'all have explained it. Rather than a separate cabin I'll just put another layer of barrier on the outside and AC the whole thing.

    I have been round and round the mountain on rim joist insulation. One thing my current home doesn't have is a water impermeable barrier between the ground and the sill plate. I pulled my rim joist insulation out because my wife was reacting to the mold in it. In my experience vapor barrier is all or nothing. If vapor barrier is done halfway, or 85% or 99 percent, there is still going to be moisture (and eventually mold) in the insulation cavities. If I could jack this house up off the continuous foundation, put in a layer of thick plastic and lower it back down I would put the rim joist insulation back in.

    My current thinking, if we go with a crawlspace, is water impermeable layer on top of the foundation, with Ground Contact Pressure Treated for the sill plate and floor joists, with insulation betweeen the joists and vapor barrier under the subflooring. This is a high dollar solution. Adding AC to the mix I could put a water barrier on the foundation, then span the crawlspace with vapor barrier, and then do the floor framing with regular lumber, insulate the joists from above and put down another layer of vapor barrier before the subflooring goes down. These are the kind of steps that give framing contractors heartburn and make them see dollar signs.

    FWIW I am sick (and tired) of floors on 2x10 joists on 24" centers. I will be building with 2x8 joists on 16 inch centers, subfloor will be two layers of 3/4 tongue and groove. This is one of those places where theory doesn't work in practice.

    For heating, since you all are sharing with me, my current dream home with the experience in the climate will be minimum 2x6 construction with outstanding air sealing and triple or better pane glass. I am strongly tempted to do a 2x6 shell to support the roof, insulate, then blue foam on inside the 2x6 load bearing studs, then 2x4 curtain walls inside that to support the ceiling, mechanicals, more insulation, then vapor barrier and drywall. Ground snow load here is 55 pounds per ground square foot, gsf. Current wind load is 90 mph but might go up when the comittee gets around to it.

    For the ceiling I want to leave all the room in the attic I can for blown in, minimum 40 inches corner to corner. Primary heat, as far as my insurance agent knows, will be a boiler on a thermostat with radiant infloor heating. I will be a "supplemental" wood stove user from the insurance perspective with pro installed chimney for low homeowner's insurance payment, and a Cold Air Intake or Fresh Air Intake installed on the wood stove so combustion air doesn't come through the HRV.

    I haven't picked an HRV (Heat Recovery/ Ventilation) system yet, but I will choose one with washable rather than disposable filters. I know a few folks who feed their cord wood stoves HRV filtered air for combustion, the finished ones have a summer/winter switch on the HRV to keep household airflow balanced seasonally. Better to put the wood stove on its own air circuit and keep the HRV balanced year round I think. I am kinda looking at trying to keep all the HRV piping inside the vapor barrier to reduce penetrations of the vapor barrier, except for fresh air in and exhaust air out of course. Hopefully I can find one that will accept cooling from a heat pump to pipe through the house.

    I did look at OWBs a fair bit, but to run them clean I would need a big tank of hot water for heat storage somewhere inside the envelope and a bunch of extra pipes and pumps and maintenance. It would be nice to keep all the cordwood chips and bark outdoors, but I am trying to get away from maintenance and there is nothing quite like laying down on the hearth in front of a raging stove after a long day out in the snow.

    Pencil plan is 3 beds, 2 baths, 2 car garage on one level. Floor plan will depend on the lot we find. We are putting a dividing wall in the garage so my shop will no longer be in my wife's garage. We will probably come in around 2000sqft, maybe a bit under.

  11. #11
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    For your subfloor, as an alternative to two layers of 3/4", Advantech, LP and other products are available in a thicker material that's really stout and sturdy. A pot framer that I follow on the 'Tube uses the LP product extensively for mezzanine type applications and it's...really solid.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #12
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    I live in Montana and am trying to finish up a shop building that has a garage (west) and workshop connected to the east with a second floor above the workshop. The shop is insulated and drywalled, and the garage is yet to be insulated (although the doors are insulated). I haven't gotten around to hooking up the mini-split in the shop because I am working out of town. We have seen low 100s here this summer. The shop hasn't gotten above 76 degrees. The walls are 2X6 with R19 batts with no vapor barrier. I did use a WRB over the sheathing. I also did a lot of research on vapor barriers and came to the conclusion I didn't need one. The primary consideration for me and the shop (as opposed to a home) was with one person working in there and no bathroom or kitchen there is very little moisture being generated inside the space. The upstairs office/studio will have a bathroom. My plan is to put a vapor barrier in the bathroom only, and I have a programmable exhaust fan that will be set to exhaust the humid air. In the longer term I plan to rely on the mini split for cooling and continue to use the wood stove when it gets too cold for the mini split to be effective.

    I don't know if any of this helps but I guess at a minimum I would consider the vapor barrier issue differently for a dedicated shop space.
    Regards,

    Kris

  13. #13
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    Scott I would certainly meet you for coffee, or at the shop. I’ve attempted to send a PM a couple of times not sure if you got them, as they don’t show in my “sent” items. Anyway let me know if you received them, otherwise I can contact you via FB.
    Cheers
    Sean

  14. #14
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    Quote Originally Posted by Jim Becker View Post
    For your subfloor, as an alternative to two layers of 3/4", Advantech, LP and other products are available in a thicker material that's really stout and sturdy. A pot framer that I follow on the 'Tube uses the LP product extensively for mezzanine type applications and it's...really solid.
    Thanks for that idea Jim. My current home has no effective water barrier between the dirt and the subfloor at ground level. I do have plastic in the crawlspace on the dirt and open cell foam on the exterior of the poured foundation. Vertically I have dirt, one layer of plastic on the floor of the crawlspace, and untreated lumber for the framing, with the next layer of vapor barrier just under the drywall of the ceiling at the second floor. At the foundation edges I have no water barrier under the pour, open cell foam on the exterior, and no water barrier between the pour and untreted framing. 1980 build, it was state of the art at the time.

    This is not ideal.

    Honestly my "best" solution is to not call the fire department right way if it catches fire so I can start over with the poured foundation and place a water impermeable barrier before I start framing.

    I am still wrapping my mind around placing one vapor barrier just under the flooring and drywall, with a second layer of vapor barrier on the exterior on all six sides to make a "thermos bottle" out of the walls and lower floor and upper ceiling. It makes intuitive sense, but executuion does not look like something I can hire out. It looks like to do it correctly I will have to do it myself.

    I am currently thinking about doing the sill plate in GC PT and then unrolling an enormous sheet of plastic barrier under the floor joists as they are installed, 16 inches at a time, so I can insulate edge to edge as I go between the joists and then install one layer of subflooring after each third floor joist goes in. In this plan I would have, bottom to top, poured foundation, thick water and termite barrier (the way the weather is going they will be here soon), vapor barrier spanning the crawl space, untreated and insulated joists, first layer of subfloor, interior vapor barrier, second layer of subfloor.

    If I do that I will have a good shot at the exterior vapor barrier. Once the wall framing is in I can just drop the exterior vapor barrier from above to the rim joists, acoustical sealant (black death) and done. But the interior vapor barrier will come out from between the two layers of subflooring, wrap around the upper layer of subflooring under the bottom plate of the walls and then come up inside the wall framing.

    Besides thermal bridging issues, no way can I get that done without having a framing crew of all old guys with arthritis poking only minimal holes in the interior VB layer and taking extra months to get the job done. If I hire young dudes to get it done quick the interior vapor barrier layer is going to get torn to shreds where it comes out from between the two layers of subflooring.

    I could maybe put single layer subfloor on the joists, get the walls up as above, and then put down the interior VB on the single layer subfloor, get that going up the walls and then put in the second layer of subflooring. I want to be able to put in hardwood flooring and/or ceramic tile, but grout doesn't stick to vapor barrier and I don't want a bunch of nail holes in the VB either.

    This is why the idea of not using vapor barrier at all and just having higher utility bills/ cord wood usage is somewhat attactive. Vapor barrier, this far north, is either perfect or not.

    I do appreciate the product lead and will investigate.

  15. #15
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    Quote Originally Posted by sean meltvedt View Post
    Scott I would certainly meet you for coffee, or at the shop. I’ve attempted to send a PM a couple of times not sure if you got them, as they don’t show in my “sent” items. Anyway let me know if you received them, otherwise I can contact you via FB.
    Cheers
    Sean
    PM'd you back a few minutes ago. Had a hunch you figured out who my wife was via FB. You are not a stalker my wife says, but my rifle battery is ready to go for anyone who is.

    The one at the the head of my bed is .338 caliber on an AR10 form factor, come on over. Just cleaned and lubed it Sunday. If someone wants to meet your maker tonight I will be happy to post my street address so as to faciliate your introduction to King Jesus. Sean is invited to ring the doorbell, but I sent him my cell number.

    May the Peace and Love of Christ be with you now and forever. Use my doorbell if you show up on the front porch please.

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