Help pick apart my construction plan

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Indygunworks

New Member
Aug 8, 2014
3
Indianapolis, IN
Sorry for the long post. I have been browsing the internet ALOT trying to find answers to the thousands of questions I have as I get ready for my new construction project. I regularly find a lot of the answers written in very easy to understand and detailed responses on this board, as well as gardenweb.com. However with my end goal in mind involving water storage and some solar I figured this might be the best place to turn.

I am sure this post is going to sound like ramblings which is mostly will be, but I am viewing the house as a system so I feel like the whole picture has to be painted in order to get the best advice I can from the knowledgeable members here.

First a bit about myself. I am 29 years old, and a full time fireman. My wife is a 3rd grade teacher and we have a 19 month old son. We were both raised in the country however when I got a job with the Indianapolis Fire Dept. I bought a house in suburbia. Long story short its not for me, nor us. We have since purchased 6 acres 4 of which are wooded, mostly cottonwood. I have installed a 300 foot driveway and a 24x32 pole barn on the property.

We are planning new construction mostly self contracted, but will hire about 1/2 done by friends in the perspective fields, but we will still be doing most of the labor right along side of them.

Current plans are a 40x44 pole barn with 15 foot side walls and vaulted trusses. Attached to that will be a 28x48 garage. the first floor of the living quarters will have two bedrooms, living, kitchen, dining, pantry, laundry, and two baths (one in the master). The upstairs will be a U with the center being open to below, and will have two bedrooms a bathroom, a living room and an 8x40 storage room.

The vaulted trusses will be 2 foot on center for attaching dry wall. the current plan for insulation is 2 inch xps under the slab, 2 inch's of spray foam on all walls and ceiling which will put the dew point within the closed cell foam so no condensation issues. then I have found a local place that sells 8ft wide by 50 foot long 6 inch thick batt insulation with a rated R value of 19. that will go in the side walls after the spray foam. the inside of the exterior walls will have horizontal perlins ran for the drywall to fasten to. wiring will be ran (maybe in conduit) along the top of one of these purlins. For the ceiling in plan on folding the 8ft wide batts into 1/3rds or so and putting them in between the trusses under the spray foam. that should end up giving me around an R 30 in the walls with the only thermal breaks being where the 1.5 inch purlins are nailed to the 6x6's. (the posts will be set on concrete permacolums by the way) and should be around an r 50 in the ceiling, but with the sissor trusses the way they are there might be some dead spaces in it. (should I add some blow in to take up the voids?)

the first floor will have a 4 inch concrete slab with in floor radiant heat. the second floor will have decking, then 1 inch (should I use 2 inch?) xps boards then tubing on top of that. I will add 2x4 nailers between the tubing and pour lightweight concrete in between to add thermal mass, then will have another layer of wood decking over that to make up the rest of the floor. (is that second layer of plywood needed? the upstairs will be mostly carpet except for the bathroom and the storage)

For cooling I have a friend that is going to come out and install to and return ductwork during construction that way we wont have to retrofit and it can be done right the first time.

Currently the plan is using a Ground source heat pump for heating (hyrdonic) and cooling (forced air). I believe I will end up with around a 3.5 ton unit. and will be using a ditcwitch to install the ground loops because I have all the open space I need to install them. I do plan on adding an air exchanger for the winter because I believe this house will be TIGHT.

The reason I am choosing the source that I am, is because last winter there was a propane shortage and it got to be around 6 dollars a gallon from the people who deliver to the area where my property is. It would be very difficult to meet the end goal of being able to get off the grid if I am relying on someone to deliver propane. I firmly believe that within 10 years the technology for solar will be in a place where I can finance enough solar, and battery storage, to end up with a monthly payment LESS than what it would be from the power company. The current electricity rate for the area is .10 per kw before the wholesale power purchacing fee, so I would guesstimate another .03 cents over that rate although I am not certain.

The garage will have radiant heat as well, however we are going to run that off a separate propane water heater that way I don't have to include it in the sizing for the heating load for the house. Eventually I might add a small wood boiler (probably home made) to supplement that water heater to heat the garage.

I considered wood REALLY hard until I realized that I just didn't have the right amount or type of wood on my land. Also, I leave for over a week at a time on multiple occasions throughout the winter to go striper fishing with my dad, and it would be fair for the wife to have to take care of that while I was gone. Indiana requires a gasser, and insurance wont let me put on in the garage or house, so for now I think my money is better spent on an effortless system, that might one day still be able to be utilized off the grid.


SO, with all that in mind, lets chat about the do's and dont's. the I wish I would haves, and I you should nots. If you see an issue with what I have planned let me know. If you have suggestions on better ways of doing things lets hear it.

Within 10 years I would like to add solar power with a very heafty battery bank. as well as solar DHW with storage. I believe if I get enough storage I can run the geothermal throughout the day while the panels would be crankin and get enough storage to last through the night. I would also add a homebuilt wood boiler to the storage that I could use in the event of a few cloudy days in a row not being able to run enough to keep the storage up. I still have lot of research to do on this whole storage thing and how it would all get plumbed together but that's something I think I can figure out when the time comes.

I plan on LED lights throughout the entire house. It might not be what I am used to and I probably wont like it at first, but after a while I think I will get used to it. I will be cooking with propane, so a full size fridge and full size freezer will really be my only other power loads. DHW will be propane as well. I own a 1,000 gallon propane tank, and will be purchasing a propane powered generator for the property as well. So cooking, DHW when the geo cant make it (winter) will be gas.

Ok, enough rambling, lets hear if I have a solid plan here or not.
 
How big is the house?
 
This is more of a DIY project. What is the green room question? Sizing the solar?
 
If you are doing radiant heat in the slab, you ought to put at least 4" of foam under it, and make sure you have perimeter insulation on that slab, or your edge losses will be high.

Why do you want to provide heat to the garage? If it is to work out there at times, fine, but make sure there is adequate insulation under the slab and inside the frost walls (if any), right down to the footers, whether or not there is radiant heat in it. If you just want to keep it above freezing so snow melts off the cars and the engines are easier to start in the cold, then insulate the frost walls down to the footers (if built that way) or provide vertical insulation down four feet or at least four feet of "wing" insulation and leave out the sub-slab insulation. That will keep the ground under the slab from freezing and let its heat come up to moderate the temperature in the garage. Insulate the walls and ceiling, and install insulated doors. My garage, in central NH (CZ6) has 2" of foam inside the foundation walls, no sub-slab insulation, just cheap FG batts in the 2x6 walls and about R30 loose cellulose overhead, with insulated doors. Last winter the coldest I saw the thermometer out there read was 37 F, even when it got below zero outside.

Be very careful about sizing a GSHP, to avoid oversizing. Your anticipated 3.5 ton unit may well be oversized for a tight house with R30 walls, R50 lid, and (hopefully) very good, low-U windows. My house has about 4000 gross sq.ft, is superinsulated to R40 walls and R60 attic floor, and the two-ton GSHP runs in just first stage to keep the house warm at design minimum temperature. My best calculation of actual heat loss at design min is 19,000 BTU/hr, vs 22,000 from my heat loss model. But several installers wanted to put in a 5-ton unit! I saw the calculation details from one of them, and they used some default assumptions in using the software packages they had. For example, there was an assumed air leakage loss of 10,000 BTU/hr from a fireplace, but the house does not have a fireplace. I do have a small woodstove on the lower level, but it has an outside air kit directly attached to the stove. It takes a real LOT of time to build a good, highly detailed heat loss model, more than most installers can afford to spend on a proposal. While their numbers may be adequate for an ordinary house, as the house gets closer and closer to the superinsulated realm a better job is really required. You don't want the heat pump to be grossly oversized. Mine is roughly twice what it needs to be for summer AC, although it has a dehumidify option on it that works well.
 
method of insulation, overall concept. Not sure if the green room was the proper place.

Insulation, solar design, heating are all good green room topics. Will the house have many passive solar features?

@DickRussell - Very good points. A home can be designed so that human body heat, refrigeration, and lighting significantly contribute to the house heating.
 
Why such a huge house? If you're trying to save energy you can certainly scale back on the square footage. Do you have like 6 kids?
 
The one detail that I noticed were your horizontal purlins on the interior walls. I live in a post frame house with horizontal purlins instead of vertical studs, and the only challenging thing has been hanging things on the walls. Make sure the architect specifies purlins at the appropriate heights to hang your wall cabinets on, and ensure there is a mounting point for things like towel racks in the shower room. The one thing that has caused the most problems for me was when two years after building it I decided to install a minisplit heat pump... I couldn't hang it where I wanted because the nearest purlin was 18 inches below it!
 
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