I think I'm building a house!

[Fordguy64]

I will certainly keep that in mind. I've been reading up and watching lots of videos on it..

[slopecarver]

I've never built a house but I've taken a bunch of notes for my future self. Note that these suggestions come from someone who has cataloged the information from the perspective of climate zone 5/borderline 6. You are in Climate zone 4 which is warmer and makes things easier.

First I want to address is the use of a Ground Source Heat Pump (GSPH). This may be needlessly complex and expensive even if using a water based GSHP. I would suggest looking into a Mini Split or the more involving path of Hydronic Air Source Heat Pump (ASHP), both with resistance heat backup for the 2% of days where they don't quite keep up. This will help you keep the installation costs lower because covering that extra 2% of heating days may cost 25% more dollars in heating capacity. You can't heat with typical HRV/ERV ducting as there just isn't enough volume flow, to get around this and incorporate the heat pump in one unit you can look into a Conditioning Energy Recovery Ventilator, or CERV. All mechanical equipment and ducting must be within the conditioned space, I don't know why idiots in the south place the AC equipment in an unconditioned attic.

To make the ASHP viable with lower mechanical costs than the GSHP you must take seriously other aspects of your construction. These include but are not limited to Insulation, Air Sealing, Glazing, Orientation, and Volume-to-surface area ratios. It seems you have Volume to Surface Areas understood with a simple rectangular structure on a basement so I'll skip it.

For insulation you want to kill any conductive heat transfer paths with appropriate insulation. Windows R4, Slab R5, Below Grade R10, Above Grade Walls R30, Ceiling R60. Source(https://www.buildinggreen.com/news-a...ulation-enough) How you go about this is up to you but there are some keywords/thoughts I can recommend: EFIS (Exterior insulation finishing system like REMOTE or PERSIST, Ignore the "behaves like" claims of spray-insulators/SIPS/ICF because they don't mean anything. You might consider adding a frost-protecting-skirt of insulation around the house, this will keep the ground around your home warmer in the winter through the top few feet of ground. Alpen Windows seem good, Consider the bug-vulnerability of various foams, if using spray insulation it should be cavity filling, Conventional building methods modified for insulating performance are recommended such as 2x6 stud walls either foam or bat filled and 4+ inches of foam on the exterior in a minimum of 2 layers without overlapping joints, You can get reclaimed foam sheets for cheap!(look on craigslist), Stay away from vaulted ceilings as they seem to be problem prone. You can increase the insulation value of a wall assembly by reducing the amount of wood in a wall since wood has an R-value of R1/inch it's about 75% as effective as most insulation. To reduce the amount of wood in a wall you can implement Advanced Framing Techniques. Other methods of maximizing the insulation/wood ratio is using a framing method such as Larsen Trusses which are used in conjunction with Dense Pack Cellulose which is another viable option for insulation, pretty simple and healthy to install too. With proper insulation and drainage the driveway can be hydronically heated in the wintertime, $4 in heat might seem like a high expense to melt a bunch of snow after a storm but the lack of ice/injury/PITA/snow removal equipment maintenance costs are your other option.

Air Sealing: Any planar meeting of tiled surfaces must be caulked with a rubbery pliable color-matched caulk to allow movement without cracking. An ACH50 of 1.5 or better is a great goal, lower is better with .6ACH50 being the Passive House minimum. When air sealing the HRV/ERV must be balanced and makeup air should be mechanically supplied for cooking vents. The ERV/HRV Exhaust should be in the kitchen and bathrooms with the supplies in closets (specifically bedrooms to keep them cooler for better sleep), you cannot exhaust the stove hood through the ERV/HRV because the grease will condensate and clog the heat exchanger. Any intake/exhaust will screw with the air balance pulling or pushing warm air against cold surfaces just asking for condensation and mold/rot/termites. Something like the clothes dryer or fireplace should be selected to eliminate this factor. A heat pump clothes dryer will take longer but not exhaust conditioned air. An HRV/CERV/ERV return should be placed in the laundry room too. A fireplace should only be placed outside, unless you use a sealed combustion self venting gas fireplace that doesn't effect you pressure balance, you won't need a fireplace to keep warm anyways because you're building a comfortable home. The garage should be treated as an outside space WRT sealing and insulating with a proper exterior door for access.

Glazing can be simply picked or difficultly picked I ask that you consider these few points: Windows can be installed with rolls of expanding foam rolls like those made by Vitaseal. Hammer and Hand has a great video on Youtube explaining the installation of a window with Vitaseal. There is a point of diminishing return where more panes of glass reduces their effectiveness and blocks more solar radiation. Position the windows at such a height that the overhangs block them in the summer and allow more exposure in the winter. Tilt and Turn windows are nice. A window should be laced at the mid-point of the insulation value of the wall, with XPS on the outside and bat insulation then the window can be fudged to the outside of the wall for deeper window sills, this helps with the turn aspect of windows not sticking too far into the house.

Segwaying from Glazing to orientation we have to consider the warm side of the house and the cold side of the house. In the winter the cold side of the house on the right-side-up half of the earth is in the north. You shouldn't have many windows on the north side of the house, they won't let in too much solar heat or light and will let out more heat than the south side windows because the north side of the house will be colder. You want more insulation on the north side of the house for this reason too! The simple way to accommodate this is to put the garage on the north side of the house for bonus insulation without the special attention you would otherwise need to give it. Bedrooms can/should also be on the north side of the house to be cooler, and quieter because you will have the volume of the living space on the south side of the bedrooms and the garage on the north side. The landscape plays a roll too, don't live on the north side of a hill, you'll get less sun and more shade from trees all year Orientation of the house isn't super critical and you can be off +- 20 degrees for lot considerations or views because I'll be recommend that you...

Ground mount the solar panes at a later date, this disconnects the serviceability of the roof with the serviceability of the solar panels allowing upgrades/replacement of each as needed. You can then place the solar panels in an optimal location on ground mounts like those recommended by Engineer775 on Youtube. He uses Schletter mounts. Ground mount offers many benefits such as cleaning/cleaning snow, upgrade-ability, expansion, maintenance (none of which are easy with a roof mount). With ground mount panels you are more free to choose your roof shape. A hip roof requires less materials.

Anything that spans I suggest going one size larger than needed. Floor truss spans, go one size up from what you specified. long window headers, one size up, garage door headers go one size up. This will remove any spring from the floor, increase the lifespan of tiled surfaces by reducing the flexing, and generally help the floor more level especially in situations where the long span is parallel with a foundation-supported-wall I've noticed especially slope-y floors. A narrower pitch on floor trusses helps here too. Roof trusses can be to code but should have high knees to accommodate your R60 ceiling insulation and an air gap for a cold roof system (this is when dealing with a REMOTE type construction system)

Larger overhangs keep the siding drier and helps immensely with cooling in the summer. You can also go without gutters with a large overhand assuming the siding is highe enough above the ground to escape splash-back. Gutters can be a troublesome spot when ice dams are likely to form, going without gutters on a metal roof that is sufficiently pitched and ventilated will eliminate ice dams, Valleys in your roof could cause ice dams to form more easily, eliminate them if at all possible.

Hallways are dead useless space, design to avoid them. Because you are spending all of this money on insulation and air sealing (orientation and layout considerations are free) you can save money on your HVAC equipment and monthly energy bills, even solar installation costs because you'll need a smaller system (this is called a pretty good house as opposed to passive house because you are augmenting the diminishing returns of super insulation costs with solar power and slightly larger mechanical systems). Cheaper than passive, more comfortable than code minimum, easier to be net-zero. Since solar is so cheap now I recommend you use only it in conjunction with heat pumps and don't use solar thermal collectors which are less flexible with respect to the energy they create, require specific installation and maintenance considerations, and generally complicate the system. For plumbing I recommend PEX implemented with the Uponor system of connections using the stretching tool. Compliment the PEX with a Home Run plumbing setup with manifold for both cold AND hot supplies with bend supports for speedy hot water delivery and no plumbing connections in walls or floors to fail. You can use PEX for the stub-outs but not for a specific distance into or out of the hit water heater based on your local code.

[Elcam84]

The two items I would do differently one just mentioned above....

I would not do a GSHP. In a super insulated and sealed house like you are building it isn't worth the extra cost. You will never recover even half of the install cost over the life of the system. In fast the best choice is actually just a plain old 94% ish furnace and a 13 seer ac. With that insulation the systems will run so little that the cost of the system is a bigger factor than the energy used by them.

In fact it's very common practice to put low efficiency units in super tight houses because of this.


The other thing I noticed I would change would be your floor trusses. 16" for that span is adequate but I'd go taller and make the floor stiffer. A floor can never be too stiff specially if you decide to install tile floors and natural tile needs a very stiff floor to keep from cracking. There is a deflection calculator over at the John bridge tile site that is very handy.

[slopecarver]

It can be difficult to find a traditional furnace small enough for a well insulated and air sealed house, short cycling can be a problem. You want it to run continuously on your 2% coldest days of the year, then you know it's sized correctly.

[Elcam84]

Originally Posted by slopecarver

It can be difficult to find a traditional furnace small enough for a well insulated and air sealed house, short cycling can be a problem. You want it to run continuously on your 2% coldest days of the year, then you know it's sized correctly.

Very true. Would probably be best to heat with radiant floor heating then one of those micro boilers to run it. That would provide heat and hot water and it can throttle down to very low settings.

Then cooling would be forced air. Wouldn't take much and ducting should be small due to the light load from insulation and it doesn't get very hot or for very long there.
Many would suggest minisplits but I would not. I do like them but they are not a good whole house choice. Takes too many units to get comfort throughout the house. IE you need to figure every room needs one. Yes the bathroom needs one. A bathroom without hvac is not a good thing.
I like minisplits for add on rooms or other hard to temper rooms. The best use of them here in tx is to put one in the kitchen. (Cool only) When the heat comes it's unbearable to cook in a kitchen here and most people cook very little in the summer because of it. The kitchen gets very hot but the thermostat is usually far from the kitchen. So when it does finally kick in the rest of the rooms are over cooled and the kitchen is trying to cool but the ac will kick off before it does. Vent hoods only take away so much heat.
So why waste energy over cooling the whole house when a mini split would remove that heat at he source and keep the rest of the house comfortable. It's how commercial kitchens are done.

[MN Renovator]

For central air in a well sealed low energy home, the furnace is less of an issue now than it used to be IMHO.

We can now buy furnaces like this one.
http://www.goodmanmfg.com/docs/libra...6.pdf?sfvrsn=0
Input rate 30,000BTUhr on high burn and 21,000BTUhr on low burn.

I think that a burn rate of 30,000BTUhr would be acceptable even for super insulated house. The reason being is that even if you have no load, a 30k furnace takes about 20 minutes to heat up about 1,000 square feet of space by two degrees. I think this is a reasonable temp rise in the winter that is imperceptible to most people. If that sort of temp rise bothers someone, a 10 minute cycle is fairly normal for a furnace and running it at the lower burn rate wouldn't be unreasonable. Furnaces like this are finally available and have more efficient ECM motors. Just a few years ago, the smallest I could find was a 40k furnace that has a 25k low fire.

This allows you to size your ductwork for the 600CFM that a 1.5 ton AC would need.

..but that's where I think the real problem lies, especially if a home is smaller. The AC load on a well insulated house that isn't packed with windows and doesn't need the cooling. A 1.5 ton AC is still oversized IMHO. I have a 2100 square foot house with double paned windows that have bad seals and are from the 80's and don't reject heat and very little blocking the sun coming in the west facing side of the house. I have a 2 ton AC and I think that with my current load that a 1.5 ton AC is appropriate for my space. ..seal, superinsulate, and change the windows and I'm oversized at twice the square footage that I would have if I built myself a house to replace my current one.

The other issue besides an oversized AC comes with the natural gas bill. How much is the fixed fee to be connected to it? I have a $3.50 fee from the city and an $9.50 fee from the natural gas provider. I'm paying $13 to have a pipe go into my house before I start buying gas. This is $156 per year. A very well insulated and sealed(I'm talking at least R60 attic, R40 walls, etc) house would probably use about this much money heating electrically. I'd skip the pipe and install the most efficient mini-splits or multi-split that I could find that work for my climate. This way you get around the oversized air conditioning issue and get the most efficient AC you possibly can and also get the most efficient heat you possibly can as well. If you go with separate mini-split systems instead of a multi-split, you have redundancy in your system if one of them goes down, which is an advantage to a central heating or cooling system such as a furnace based system. You also don't have the labor expense of ductwork or hydronic either. I think the cost of multiple mini-splits in a system would be a wash to putting in ductwork or a hydronic system, both types of pipe are a pile of work, even more so the hydronic.

[pinballlooking]

Here is a netzero retirement community.
Building Passive Houses and they almost always use mini splits.
A good read no matter what.
Ankeny Row | Home Power Magazine

[Fordguy64]

Well that's a lot of good info. I've been doing a lot of thinking about the radiant floor lately and I'm kind of leaning towards not doing it. I'm not sure if the 15k price tag will fit into budget. It's not even just the 15k tag it's the fact that I will still have to install mini splits or a central ac unit to cool/dehumidify the house in the summer.

I have no plans to hook up to a gas line. As the monthly fees are annoying for the amount of gas I would use.

As far as what kind of system I will end up installing I don't know just yet. But a small geothermal system won't be to $$. As I can dig the trenches and things myself. But the duct work will obviously add cost to that instal. But I think with the floor joists that I plan on running the duct install should go much faster

Thank you all for the input and ideas KEEP IT COMING!

I have also thought about putting some cheap heat and ac in and then hacking a system to take over for the long run. Maybe a 3 phase variable speed geo heat pump?

But I'm just not sure i will ever have time for that with building a house and garage.

[Fordguy64]

interesting info on pump and dump with a pond.

[stevehull]

Like I said before - really look into open loop GT heat pumps. You are on a well - why not use it?

Secondly, your house insurance goes down when you have a pond (and are not within city limits). A pumper can drop a suction line into the pond and have almost unlimited water. House insurance like 30% less . . . . .

When you have a lot of quality sub-surface water (which you do) and you already have a well, it is a simple jump to a pump and dump (open loop) GT heat pump.

Your cost is < $3k for an open loop system.

Steve