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MEMPHIS builds a house
So I never thought I would say this but we now have plans on moving, the current location/house/stress is not what we want. So we have plans on moving to another county (this one is getting way to strict in all the wrong ways). Looking at a 1,500-1,800 square foot 3 bed 2 bath house with a 10x12 (not heated and cooled, just insulated) basement/root cellar. I want it to be as efficient as money will allow, I will doing most of the work myself as NO one in the area knows how to build a tight super insulated house.
Thoughts so are: -2x6 exterior walls on 24" centers with 1 of spray foam and the rest filled with fiberglass or cellulose -3/4 ridge foam wrapped, with 1/2 osb sheeting on top and then wrapped in a good moisture barrier/air seal -roof with 3/4 ridge foam and vertical 1x4's strips to allow the silver tin roof to vent. -vented brick exterior -dense packed cellulose in the ceiling to about R40 -insulated slab floors (though I am finding places saying uninsulated is better) -vinyl 9mm fake wood tung and groove flooring -5 total mini splits 2 of these for where we will be most of the time Gree Crown 9 000 BTU Ductless Mini Split System Remote 25' Lineset 208 230V | eBay and a set of these for everywhere else 27000 BTU Tri Zone Ductless Mini Split Air Conditioner and Heat Pump SEER 23 | eBay -Looking at this hrv Panasonic FV-04VE1 WhisperComfort Ventilator, ERV -There will be a wood fireplace for back up heat -all led lighting wired 12v -all dc ceiling fans (each bed room and one in the great room) -heat pump water heater in the basement/root cellar -good at least triple pane windows with double low e coatings My goal is to make a house that isn't out of the park expensive but can still out perform 90% of houses built today. I think I am set on no geothermal for the main house, I might put in tubes in the floor just in case I want to build a DIY geothermal heated floor for the main rooms of the house. I am doing tons of research into how to position the house for best solar My cooling days are more than my heating so im looking into how and where to add radiant barriers. Opinion on if a should build in a way to prevent thermal bridging? Or is it not as big a deal down south? Any tips, tricks, or links would be awesome. This is going to turn into a long long thread as I post building pictures and as always a step by step over view. Thanks guys and Shalom |
I would highly recommend you go with non-wood SIPs (Structurally Insulated Panels). May cost more for the materials but time, ease, and insulation value is not beatable.
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natethebrown, I am looking into them now, why non wood? https://www.youtube.com/watch?v=QhOYlHG_aAc
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Don't obsess on PV solar roof orientation. So long as a roof area is within 20 degrees of true south each direction, this still gives you 90-95% of true south solar power.
Mistake on triple pane. In your southern climate, you don't need it in the winter - money spent here is a FAR too long payback. Double pane is certainly enough - but buy good ones, not the locally built vinyl clad cheepos. But you DO need to pay attention to summer overhangs on east, west and southern windows to prevent solar gain (maybe this is where you meant orientation). In your area, do NOT insulate slab as you need to bleed off heat in summer. Your ground temps are just not that cold in Mississippi. Outside air moisture and interior humidity are your enemy. Put your dryer in a room with outside air inlet and seal it off with good closing (sealed) door. A dryer pushes some 500-600 CFM per minute out of the house and conditioned air pushed out means that air (humid/moist and hot) MUST come in as house is now a vacuum. Two ERVs are a necessity with a tight home of this size. The ones you are looking at are great in bathrooms to vent moisture 24x7 and total also provide about 40 CFM total (low speed). When bathroom/shower is in use (DPDT switch to bathroom light), then HRV goes into high fan speed mode (total 80 cfm). I would still do geothermal for ducted AC . . . . an open loop system. You need to put in a well anyway. That many minisplits gets you into expensive territory. I have recently bought from Ingrams and they have a very nice three ton GTHP for about $3100. Forget the thermal heated floors - you just do not get that cold to justify that cost. I would do SIPS for roof as you get everything for not a lot of $ and will be installed in one day (roof decking, insulation, interior trusses, R40 foam and inside OSB). SIPS with 8 inch foam (R40) are easily available. You can get 12 inch, but your local conditions don't merit. You can span up to 40 feet with SIPS. Makes interior layout easy with no load bearing walls needed. Infiltration is your enemy - not heat or cold. Build yourself a temporary blower door (or window) with an old HVAC squirrel cage blower and simple water manometer. I use dry ice for "smoke" to detect leaks. If you are in a rural area, build a pond (discharge water from open loop geo unit into this) as this markedly lowers your home insurance. Home insurance goes WAY up in rural areas with volunteer fire departments. You will also get a discount for metal roof (good idea). A fire pumper can dip suction hose into pond. Pond got me a 30% discount on my home insurance . . . Do you really mean "as efficient as money will allow"? Why a fireplace? This is a true energy waster. Put in a good wood burning stove that has opening (and closing doors). You can see fire if you want to, but can close it up for more efficient use. - but make it small (24 - 36 KBTU/hr) as it will otherwise overheat the house. Mazel tov! Steve |
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Here are some old pictures of my dad's addition (his addition is about 95% complete now): http://i78.photobucket.com/albums/j1...rown/SIPs3.jpg http://i78.photobucket.com/albums/j1...rown/SIPs2.jpg http://i78.photobucket.com/albums/j1...rown/SIPs1.jpg You can see each SIP is about 4'x10'x~1' thick and is light enough for two people to handle. Any ways, if you decide on wood SIPs, no problem, I just believe the "standard" stick frame home is out of date and so low tech compared to what building technology we have now. |
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natethebrown, Yes the more I look into SIPs will play some roll in the building, thanks for the awesome idea. I will look into the cost comparison with wood/non wood. Good pictures as well. :thumbup:
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I have successfully used sub-slab supply ducting (glued PVC) and as a side benefit it really heated up the concrete slab floors in the winter (dogs loved it!).
The old metal ducts clearly don't work (they always rust out), but the glued 8 inch long tube type PVC ducts are absolutely watertight. Not hard to do and now the supply ducts are completely out of the way - and there are NO air leaks. You can do a common air return and/or return "jump" ducts into bedrooms and other closed off spaces. Your RFD and/or insurance carrier can tell you the amount of water that qualifies for the discount. In my case it had to be a 1/4 acre pond at least an average of four feet deep (total of one acre foot) and had to be there all year round. Be realistic and do what you can do. Hire out tedious stuff as otherwise you will have a two year build phase or never quite have anything done. Remember that construction loans are only for 365 days. All is simple, but there is an advantage to getting pros to come in to quickly get you dried in. With SIPS, this is no more than two weeks. Also, hire out the brickwork - they are just so damn fast and perfect. Have fun! Steve |
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A GTHP does several things. First the summer SEER is 35+ and you get free hot water from the desuperheater. The winter heating is easy as the COP is 4+ and you get hot water as well, but not as much as in the summer.
Ingrims is the key. A 36 K BTU/hr GTHP for $3400! Misc supply PVC is another $300 or so and you can glue this together. Then some supply boots put in before you do the slab. This is easy work. Two (2) Stage Geothermal Heat Pump Buy Goodman Heat Pump | Geothermal Heat Pumps | Goodman Air Conditioner The minisplits are great, but they don't seem to last that long . . . . . Some of my GTHPs have been going since 1991 with no fixing at all (except air filters). Steve |
The Double stud wall is the cheapest to build but I don't think it is the best wall. if you are ok with foam, you may be able to find used foam insulation for cheap enough that a double stud wall may not make sense, especially if you are the labor supply. There is also adding foam strips to the interior of the studs with a 1x on the interior side for a nailing strip. This can add a bit more cavity depth and also reduce thermal bridging.
As far as sub slab insulation is concerned my inclination is to say either that or perimeter insulation is a good idea. however I would hire Energy Vanguard or some other firm (Allison Bailes at energy vanguard can probably recommend someone if they can't do it) to do some energy modeling and cost optimization. Now is the time to start that conversation as they can help you avoid design issues that can cause large energy penalties. As for GTHP, I'm meh on them. great concept, not so great execution. The other issue I see judging at least by the ingrams site is that they really don't have something small enough for your situation. I'm betting if you build your house well you will see an AC load of around 1 ton. Heck even finding conventional equipment that small can be a challenge. The majority of your heating and cooling hours will be at part load conditions, this is the area that mini-splits excel at, and where they beat GTHPs. Quote:
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Steven those numbers are for sure nice, I'm still concerned with it being over sized, but at that price your right it is hard to beat. We are not stuck on the mono pitch yet. I think as long as we have vaulted ceiling in the great room/kitchen area we would be happy. I still hate the idea of having my duct work in the attic unless of course I can have the rather a insulated, but then I hate the idea of heating and cooling my attic. So many options, so much more research. I wish more people had these type systems/houses in my area.
DEnd, I am really liking the idea for sips they seem quick and a good product, I'm going to do some calling around to see if anyone in the area builds with them. I have a lot of connections around here. I can make more money at my job than I can save doing the time consuming labour parts of the house. I'm the general contractor for sure though. Thanks for all the input guys. |
If you are concerned with oversize at 3 tons, then put in a two ton unit. The key is the two speed compressor. Most of the time the GTHP will run on stage 1 (lower compressor setting). This maximizes water extraction and maximizes efficiency.
Remember that minimal human activity, electronics, appliances and cooking can easily add one ton of cooling. And cooling is your 80% issue - not heating. This is on top of the manual J load. So if the house, by manual J, is one ton, then you really need two tons for the most basic cooling issues. Cooking is a major contributor. Second is electronics and appliances in terms of providing vampire heat load. People are significant and significant heat, but a LOT of moisture. Remember that cooling load is just not heat, but also indoor latent humidity in addition to that which is outdoors (and leaks in). I am just not seeing the longevity with minisplits as compared to GTHPs. I also REALLY like SIPS for speed of building, envelope tightness and strength Steve |
Mono roof pitch is easy to build, easy to put metal roofing panels on, and provides roof at the minimal sq foot area, but can be a problem in providing shade. A reasonable pitch (3/12) means that a significant southern overhand is wide. And this means that your southern roof line at the eve must be high. Otherwise, you hit your head on it.
Make no mistake, I really like a flat pitched roof - especially if it is a SIP roof. It provides great interior height. But it also means a very high northern wall at the roof high end. I am assuming that the roof will pitch to the ~ south. That means the north aspect of your home will be your high side. Because SIPS can span a large distance, it is not hard to do a standard gable roof with just SIPS and not needing trusses. A bit more roof surface area (compared to a mono pitch) to cover a given house footprint. A mono pitch roof is great, but you need to build one VERY tall wall. And that is more expensive than a few more sq feet of roof area. Assume your low wall is at 10 feet and your home is 24 feet wide. This means the high wall must be 16 feet high. This is based on a standard 3/12 pitch. Lots of trade offs . . . . Steve |
OK so now I'm 50/50 on Geo vs mini splits. So monopitch is out now. We will have attic space for ducts if needed.
What type well pump do you use for your open loop Geo systems? |
I have a 1.5 HP 220 V single phase deep well pump - but I am also watering livestock and my water table is down almost 70 feet. If I recall, your water table is much higher.
My well pump is supplied by my solar panels. Why not just put PVC supply tubes for HVAC under slab? That way, you don't have to use hot attic for supply ducts. You have time to decide on MS vs GTHP. Steve |
Would the PVC ducts in the floor need to be insulated? Would the slab then need to be insulated? I like the idea just don't want to add tons of cost. Is doing a well pump going to off out the geothermal savings? I just am having a hard time seeing a pump run for that long without drawing a lot of power. The discharge/pond idea is great though. I can solar power mine as well, and one day plan to, but that is a huge extra cost. Thanks for all your advice its going to help me make the best choice.
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I did not insulate my sub-slab PVC ducts and my ground temp in Oklahoma is about 60 F. You are a few degrees warmer. I did look into PVC duct insulation and the cost was way too expensive. I did not insulate my slab. Absolutely necessary up in the cold north.
Of course you will need amps to run a deep well pump, but you don't need pressure and you can run a GTHP on 10 psi. Then have a separate "booster" surface pump to do 60 psi for home use. The alternative to an open loop (aka "pump and dump") is to put in expensive vertical wells or did like crazy and put in a huge loop field. Lots of time and or $. Solar, to run a pump with a grid tie, is NOT expensive. If fact, it is so cheap that you can't afford not to do it. Your 20 year lifetime kWhr cost will be a fraction of the current retail kWhr cost. But you did confirm, "as efficient as money will allow" . . . . . I would do open loop geothermal, a 10 kW solar system and a SIP home. You are FAR better to do solar PV and efficient heating/cooling now. If you install yourself (not hard) the cost is about $1.1 a watt. Then the 30% tax credit - so the real cost is about $0.75 a watt. This means about $7,500 to put in a 10 kW PV system, let's say $4K for a GTHP (including ducting). That total is under $12K. Pay someone to do this and add another $20K. Typical charges to put in a grid tied PV system are $3+/watt. Start by setting yourself up for savings and then put other important stuff around it - like LED bulbs, SIPS, tight house, ERVs, etc. Think strategically - not tactically . . . . it is all about saving money down the road. Lastly, what you pay for electricity is AFTER tax money. Lets assume you are in the 20% IRS bracket (being conservative). To make $100 in take home, you have to make $120. But you pay for all stuff AFTER taxes. That is why money saved is such a boost. Steve |
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I don't really have anything against SIPs, but their details are not common knowledge. Yes they are fairly simple, but finding people who know how to move the Sips efficiently and safely as well as detail any penetrations they have, and know the tricks of wiring etc... is a lot harder than finding people who are familiar with the details of stick construction. I would say you need some form of slab insulation regardless. At minimum you need to address the thermal bridge at the outside of the slab. BSC has a few ways to do this: https://buildingscience.com/document...059-slab-happy |
I would like to throw out a few design ideas at you. One of my favorites is Away space. The basic idea is that you provide a lounge/work space for each member of the family. Say you have two kids, that is an easy one, you provide enough space in the bedroom for a chair and desk, then for each of the parents you provide a space in the master for a chair or two and then you have the living room. But what if you have three kids? well you could do a fourth bedroom, but a den/home office might be worthwhile instead. Even with just two kids a den/home office is a pretty good Idea. Because, lets face it what parent wants to be subjected to Spongebob when they are trying to get the bills paid?
Does someone work from home? If so (or if it is a possibility) then the placement of the home office is critical. This space should be somewhat private away from the noise and distractions of the rest of the house. I tend to like the front rooms of a house for this. It can be placed in a way that the kitchen is basically concealed from view for any clients that may come by. Also having a formal dining room at the front is fairly popular now as well, this allows that space to also be used as a small conference room. I like the idea of having a kitchen in a separate space from the rest of the living areas as well. It can still be open to those spaces but make sure it is out of the traffic flow. I also would recommend having a full bath available on the first floor, preferably one that is laid out with wheelchair accessibility in mind. Along with this have a space that can be converted into a bedroom. Speaking of kitchens and baths, they are the most expensive square footage in a house, limiting their size and numbers is a great way to save money. That said layouts that work well even if a bit larger are worth the money. |
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Memphis - the price I quoted you on PV solar is a complete system (panels, inverters, racking, wiring, etc) - just no install labor. Right now, after tax credit - about $0.75 a watt.
A lot of people simply can't believe this - but I am quoting you actual numbers. Steve |
You got a examples? I can barely find 10k of panels for $7,500 (with 30% tax credit). That is awesome news!!! Sounds like open loop/pump and dump system will be making its way to the 60% likely now.
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I am quoting prices that are on the Renvu site right now - not specials, but regular prices. I forgot, shipping is extra - add another $500.
I see 260 watt panels at $0.64/watt and microinverters (Enphase M215) at $98 each. Roof racking is about $28 per panel. Trunk cable at $17/panel. Add it up . . . This weeks RENVU special is the M215 at $86 and also cheaper panels. renvu.com | Search By Steve |
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I haven't done any research on it, but if I was to take a wild guess at it, I would probably go with a minimum of 36v DC circuits. You can get 36v LED COBs on Ebay for cheap, you just have to attach them to a heat sink. |
Steven, your right, I guess I was looking at over priced sites, that is not a bad deal at all. Do they make inverters that can charge batteries just in case I want to have back up power?
Nathan, thanks I'll look into that |
Just found this https://enphase.com/en-us/products-and-services/storage
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Memphis - to get an idea of the amount of perimeter BTU leakage, first get the peripheral area that is exposed. This might be one foot high all around the house. Assume 300 sq feet.
Then multiply that by the temperature difference between inside and outside. Lets call the interior slab 70F and the outside 50 F. That is a 20 F difference. The concrete stem wall already has an R value of 2-3. Now go look this up in the manual J calculator and you will see that it is a very few BTU/hr. However, in the summer, you "bleed" BTUs into the soil (soil cooler than slab) and a non-insulated slap helps keep the house cool. You are in a dominant hot area and your winter load is very low. I figured that my noninsuated slab basement was about 12-15 KBTU/hr in terms of cooling. Yes, the floors were just a bit cool in winter, but we had throw rugs down there. If I had all the money in the world, I might insulate everything - but time is also an issue and you want to build this before you die . . . Again, you will do what "allows you to sleep at night". For some, in a moderate climate, this is R100 - for others it is R40 (just picking an example for attic insulation). AC has some very nice tables that have cost/benefit intersecting lines on it. Study this concept. Now look up the cost to insulate the entire periphery and see how much you lower your BTU loss in winter. Will not be much. The entire issue is to do perimeter insulation in climates where it is a MAJOR cold area. You just are not that cold and your "frost" depth is on the order of inches. You can do the same with sub-slab duct insulation. But remember that if using a GTHP, that the supply temp is only 100-110 F. A standard gas fired heater has very high hot air. So in the case of sub-slab, the delta T is 105-65 = 40 degrees F. If the dirt under your slab is kept dry (which is typical), then there is "insulation" around the PVC duct Now look up the cost of closed cell duct insulation and gasp. I found it was not worth it IN THE SOUTH. The reason I am doing this in caps is that we have people from tropical areas all the way almost to the poles on this site and insulation is highly regional. One size (or advice) does not fit all. Steve |
Steven, your information is amazing, and I'm sure that many other builders/ renovators are going to use it for years to come. It's hard to find info. I'm all about cheaper. And yes you are right the frost line is not much at all here. I will not insulated my basement/root cellar any way because I want it to be the temp of the ground.
I'm still concerned on duct because of the length of the house. I may have to use 10" in some places. Or 2 10" lines with other lines branching of with 8" and 6". That is just a matter of running the numbers though. And if I go with a deauperheater, I really want my hot water tank in the same room with my unit. And right now my house design does make room for that. BUT that can be changed. |
We are looking at electric oven with warming oven above it. these will be mounted into the cabinets. My idea is to place prelite/rockwool insulation in the air space sounding the oven (in the cabinets not directly touching the ovens. This would be built so that the oven could vent and operate as normal, just not be heating up the air. Less energy needed to keep the oven at temp (I like my texas toast and that means an oven at 450-500F!) And heat the air in the kitchen less.
Also has anyone ever thought of hacking a mini split for geothermal? I am thinking I should go with a 2-2.5 ton 2 stage geothermal and at least one mini split that can at as a dehumidifier running on very little power. |
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Jeff, yeah because a stick of 8" sch40 20' pipe is $130. I be on the look out for cheaper.
I really like the idea of hacking this mini split water chiller to make it geothermal. But the cooling is only 2 tons. I think the house is going to be closer to 1,500 square feet though so that might be doable. And if not I could always put in an extra mini split. |
Menards has 10" x 10 ft sticks on sale now for 49 bucks a stick. The fittings is what gets you.
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There is a $500 rebate I will miss out on if the duct work is in the ground. Bottom of this article. https://www.2escore.com/Documents/HVAC_1114_v6.pdf
Might just be better to go the the attic space. It will be in the envelope anyway since the house will have a sip roof. Though I really like the warm floors idea of them in the floor. Total duct work in the floor looks like close to $1,500 for pipe and fitting. |
I Love my bathroom layout. It is the width of a standard tub/shower unit, installed at one end. The other end has a clothes washer and water heater. The door and window are opposite each other next to those. That provides a handy space to change, with hooks on the door and the washer ready to help as both laundry hamper and table. Fresh, sorted laundry is on shelves above the washer. The tub has a clothesline, adequate for a load on hangars, and the heat duct blows on them. The window wall has the toilet beside the tub, with the scale nearer the window. The door wall has a vanity with a gap beside the tub. That space has the waste basket, toilet roll and magazine rack. While seated, I can change the toilet roll using the waste basket and supplies from the vanity. I can also wash and dry my hands, with a towel over the shower curtain rod. The door swings in, and has a big mirror. When the medicine cabinet door is open, those two give an adjustable rear view. There's only enough floor for a couple of small bath mats, but it does the job without a hitch.
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For the heat pumps, I think you are planning on oversizing your system. With good air sealing and well designed ductwork you should be able to get the system size down to below 2 tons. You already know my thoughts on dehumidifiers, but I don't see a reason to go with an inverter controlled compressor here. Moisture loads out side of kitchens and baths just aren't variable enough to justify the expense. |
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Bob, That sounds like some really good ideas for sure, we have been looking at tiny house plans to get ideas like these you suggested in order to save as much square footage as possible. Thank you.
DEnd, This just doesn't make since to me, I do understand the controls don't need to get to hot but the stoves have thermostats, insulating areas that already have it/need it will only cause the stove to heat up quicker and therefore use less power. All modern stove are vented, some through the top of the door, some through a pipe under one of the back eyes (on ranges) and some through the back (I'm sure others have other places as well). As long as the stove is able to vent the way it was designed I would think it would operate correctly. If I have to I can add some shielding to the controls and maybe even a couple extra vent holes for better air flow to them. This is just what I think, please blow my logic to pieces if I'm missing something. The last thing I want to do is burn down the house. UPDATE: Land will be closed on on NOV 14th, we are buying 93 acres in Pontotoc, MS. This land is amazing. It has creeks that run all year for possible microhydro, great dirt for gardening and a vast amount of diverse land features that will provide tons of project ideas and homestead. I've been reading up on the Mixed-humid 40% saving manual, it has some really good info. Building America Best Practices Series Volume 16: 40% Whole-House Energy Savings in the Mixed-Humid Climate | Department of Energy |
It's the electronics, and wiring that need to be kept cool. Insulating the air space around a built in reduces the amount of heat rejection that is needed to keep these components cool.
The other part is ovens are just like houses, good insulation and air sealing reduces energy useage. The weakness in ovens tends to be the air sealing at the door, the thermal bridging there, and the reduced insulation (due to the glass) at the door. Self-cleaning ovens tend to have the best insulation. Ovens with door locks can reduce air leakage, as long as the door lock works to apply pressure on the door. Adding insulation could help, but you need to add it to the oven and keep wiring and electronics outside of it as much as possible. I do agree that most ovens are underinsulated. |
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