Energy Efficient House Design

[Tom Bender]

We are very pleased with our house design. It runs very low utility bills for Michigan. It's pretty basic;

Ranch with full unfinished basement, one ceiling level, nothing vaulted

No sliding glass doors or skylights

No fireplace

3 1/2" fiberglass in the walls and 12" fiberglass and blown in in the ceiling

Foil backed drywall serves as a moisture barrier

Old standard efficiency forced air gas furnace

Gas water heater and stove

Attached garage

Good doors and windows properly installed

[Frederick Skelly]

Sounds good Tom. Lotta smarts there.

[Perry Hilbert Jr]

Just built a new house 2 years ago. two story over 2,500 sq ft. with full unfinished basement, insulation, fancy windows, LED lights where ever possible. Two furnaces, one for upstairs one downstairs. Propane for heat and cooking from June 30, 2016 to July 2, 2017 was $489.00. Thing is, there are so many other things we could have added. A buddy has an old brick house with slate roof. He put a circulator fan in the attic, so when heat hits 90 degrees in the attic, the warm air is circulated through the house, if the house is under 72 degrees, or outside, if the house is above 72 degrees. Saved him nearly a third off his natural gas bill in one year. My grandparent's house had a brick wall in the kitchen that had a southern exposure. The heat from the sun hitting the bricks helped keep the kitchen warm in winter and spring. Outside was a grape arbor that shaded the brick wall in summer and fall, helping keep the kitchen cool. Guess Grandpop, a cabinet maker by trade, who died in 1956, was also an energy engineer.

[Brian Elfert]

A properly sealed house shouldn't be allowing the attic to hit 90 degrees during heating season unless it is heating up due to solar rays hitting the roof. I had the insulation pulled out of my attic and spray foam applied to seal all the air leaks into the attic. A foot of blown-in fiberglass was placed on top of the spray foam.

[Stan Calow]

Amen. Its hard to find new efficiently designed ranch homes around here despite increasing numbers of old retirees who want them. Builders tell me its too costly per SF because of the relatively large foundation size. So they build mostly cheap starter homes and multi-story McMansions.

[Brian Elfert]

Most home buyers buy the looks, not the mechanicals and insulation. Shoppers for starter homes are very price sensitive and an extra $5,000 for better efficiency will send them to the other builder that is $5,000 less, but not energy efficient. Most buyers would much rather spend $5,000 on better interior finishes before energy efficiency. They can show off the fancy appliances and granite countertops to friends and family, but they can't show off upgraded insulation.

Here in Minnesota there is state code requiring more energy efficient houses. My house was built in 1980, but I remodeled it before I moved in. My total gas and electric bill for a year is $1,250. Previous owners paid $3,500 a year because of all the air leaks and such. My ideal house would be built with SIPs, or at least have spray foam insulation.

[Bill Dufour]

I am surprised you can get away with so little in the walls in your climate. In most of California you would have to add styrofoam over that wall to meet insulation code minimum.
Bill D

[Jim Becker]

Bill, 3.5" in the wall can be as much as R15 these days and depending on the sheathing type, the wall, itself, could get into the neighborhood of R19-R21. 12" of blown-in Fiberglas up top should theoretically be in the neighborhood of R30-32 if installed correctly and many times is higher because of being over-blown. Depending on when the OP's home was actually built, he's sitting pretty good. Only new construction or major renovation generally triggers the higher levels that are now code in some areas.

[Bill Dufour]

Bill, 3.5" in the wall can be as much as R15 these days and depending on the sheathing type, the wall, itself, could get into the neighborhood of R19-R21. 12" of blown-in Fiberglas up top should theoretically be in the neighborhood of R30-32 if installed correctly and many times is higher because of being over-blown. Depending on when the OP's home was actually built, he's sitting pretty good. Only new construction or major renovation generally triggers the higher levels that are now code in some areas.

I guess my info is from watching houses built in the 1990's around here. I have no idea why California still allows R13 instead of R15 fiberglass in the walls. I have a feeling the builders have paid off the law makers.
Bill D.

I know our friends in the mountains at Truckee have much more stringent codes for insulation and snow loads then much of the country.

[Jim Becker]

What applies to new construction and major renovations doesn't apply to what was installed years ago. But yes, sometimes localized codes don't make sense, like permitting R13 insulation, when R15 is readily available for almost the same cost. Same with regard to R19...R21 is readily available and fits in the same space for about the same cost. But it wasn't so long ago that R11 was still permitted in walls... go figure!

Me...I'm a closed cell spray foam fan. R7.5 per inch. :) Adds rigidity and is a nearly complete moisture barrier. Costs more up-front, but the payback can be relatively quick in many geographies based on average weather and energy costs.

[Steve Peterson]

The OP listed lots of good points. Another important point is to have a modestly sized house. I was perfectly comfortable growing up in a 1200sf house. It seemed big enough at the time. Even with 1950 style insulation, the heating bills will likely be smaller than a modern 4000sf house.

[Matt Meiser]

As a fellow Michigander I'm surprised at the 2x4 walls. I've considered building each time we've moved and wouldn't do less than 2x6. We lived in a 1991 ~2000sqft ranch for 11 years and moved to a 2003 ~2200sqft 2-story about 3-1/2 years ago. The ranch we added insulation in the attic and while it cut our utility bills slightly we found the house to be less comfortable because we actually found the house less comfortable because our bedroom stayed too warm at night in the winter! Probably a mixed bag on benefits and drawbacks. One reason I don't have a shop anymore is the surprisingly smaller basement of a 2-story. The big, bright 2-story foyer in our current house is a worth any "wasted" energy to me. Upstairs gets awfully warm in the summer, but its nice not having guests walk past the master on the way to the bathroom, not having our daughter's bedroom literally 10' from the living room and not having her bedroom across from my office is nice. Also it takes a lot less time getting hot water from as much as 60' away to a bathroom but doing a project that requires getting utilities from the basement to the upstairs is a pain. Even running a simple Cat5 cable is time consuming. Lastly, I wasn't comfortable getting on the roof of the ranch and there's NO WAY I'll get on the 2nd story roof! On the other hand the TV antenna that had to go on the roof of the old house works just fine in the attic here.

Utility costs are difficult to compare as we added natural gas and a heat pump at the old place the last couple years. Our bills here are probably higher here with run-of-the-mill furnace and AC but not enough to spend money on improvements.

[Jim Becker]

Matt, I don't disagree, but with closed cell spray foam, you can balance the lower material cost of 2x4 walls with the higher initial cost of the insulation and end up better than you would have with 2x6 and conventional insulation...and the stiffening that the foam provides makes the walls very, very sturdy. We did that with our addition here in 2008 and the cost was not quite a wash. Only one small wall area was done with 2x6 and that was to better assist with space for utilities, etc.,

[Pat Barry]

We are very pleased with our house design. It runs very low utility bills for Michigan. It's pretty basic;

Ranch with full unfinished basement, one ceiling level, nothing vaulted

No sliding glass doors or skylights

No fireplace

3 1/2" fiberglass in the walls and 12" fiberglass and blown in in the ceiling

Foil backed drywall serves as a moisture barrier

Old standard efficiency forced air gas furnace

Gas water heater and stove

Attached garage

Good doors and windows properly installed
It honestly doesn't sound all that efficient. It sounds like any old house anywhere for the most part. You don't mention the square footage or actual cost to heat and cool the building for example, or draw any comparisons to what you deem as typical utility bills for your area. You don't mention what temperature you heat / cool to. Lots of missing info to make any conclusions from in my mind. Assuming you are correct though, what do you think is giving the biggest savings in your utility bills?

[Larry Edgerton]

I am building one now that has a 3/4" dead air space on all exterior walls and a 1 1/2" dead air space on all the ceilings, steel frame, urethane foam walls and ceiling, infloor heat with both gas and solar heat sources, and Marvin all ultrex windows. Curious to see how it heats/cools.

[Nike Nihiser]

That dead air space won't do you any good unless it is virtually airtight, other wise it's just a path for drafts.

[Larry Edgerton]

Hence the "Dead" part of dead air space.

[Mac McQuinn]

Hence the "Dead" part of dead air space.

Nicely put, :)

Mac

[eugene thomas]

Not sure why would use 2x4 outer walls in new construction. ??? Sure when selling some buyers will probally wonder same thing.

[Jim Becker]

Not sure why would use 2x4 outer walls in new construction. ??? Sure when selling some buyers will probally wonder same thing.

Common with spray foam insulation as I've already noted. The major reason for the general shift to 2x6 walls is space for insulation and with closed cell foam coming in at R7.5 per inch, the extra cost of the thicker walls isn't necessary and helps to balance the cost of the insulation. But with fiberglass or other materials, I agree with you...no way would I accept 2x4 walls.

[Malcolm McLeod]

Spray foam and typical 3.5" stud wall will give you fairly noticeable thermal bridging (in ~9% of you wall :: 1.5"/16"). IIRC studs have R-value of ~1.5/in. For full benefit of foam you need 2x4 wall studs staggered in/out on 2x6 plate - or something equivalent.

Also, keep in mind that with improved insulation and air-tight windows/doors, you can get indoor air quality issues. Today, its relatively easy and (sorta?) economical to insulate to the point that you'd need makeup air blower with air-to-air heat exchange on it.

There will always be a balancing act between costs: installation vs energy use vs live-ability (health).

[Pat Barry]

I am building one now that has a 3/4" dead air space on all exterior walls and a 1 1/2" dead air space on all the ceilings, steel frame, urethane foam walls and ceiling, infloor heat with both gas and solar heat sources, and Marvin all ultrex windows. Curious to see how it heats/cools.
I'd be curious too. Where did that idea come from. See, the whole point of insulation such as fiberglass is to create lots of small, disconnected, dead air spaces. Large dead air spaces are actually quite prone to convection air currents.

[Larry Edgerton]

Pat, this house has all kinds of unconventional thinking. The dead air space is inside 3 1/2" of polyiso foam, and serves two purposes. One a disconnect between the outside insulation and a path for wiring so that the outside envelope does not have to be compromised except where boxes are routed in. It allows 2" of foam behind boxes. Also the air currents do not make any difference as each individual section is sealed and so the and so air is not taking a part through the wall cavity but rather just moving around.

I have been doing dead air space ceilings for years with a sealed layer of 1/2" polyiso HD, 3/4" strips, all caulked in and then drywall. The results have been amazing and no problems with trapped moisture. This is the first time I have done it on walls, but this is an experimental house, so why not experiment? I have to admit the wiring issue was the catalyst but I am curious by nature. I have probes installed in the wall that allow me to keep track of the temp and humidity of the air in the airspace in the wall.

If no one tries anything new, nothing changes.............

[roger wiegand]

We did a deep energy retrofit on our 1950 garrison colonial that was an energy hog and added a 1000sf addition built to modern specs. The list of things we did was long, but included wrapping the old part of the house in 2" of blue foam, sealed and taped zip wall sheathing and insulating the 2x4 walls with cellulose, new windows (not "replacement" windows), spray foam in the attic and rim joists. and foam, 2x4 walls with fiberglass in the basement. The addition was panelized construction with 2x6 studs 24" oc, spray foam inside, rigid foam outside for thermal bridging, blown cellulose in the attic. We were fanatical about air sealing. Heating is a conventional inexpensive forced hot air furnace with zoned dampers. We installed an ERV for air quality and used sealed combustion furnace and water heater to prevent backdrafting.

This wasn't the "passive haus" level of cost or complexity, but seemed a reasonable compromise. Doing it again I'd probably go with staggered doubled 2x4 walls with cellulose rather than the spray foam for the walls.

The house is incredibly comfortable, with no drafts or cold spots. Our biggest complaint is that it won't cool down to a comfortable sleeping temperature at night, so we end up opening a bedroom window in midwinter.

Bottom line is it works; here's our energy report from a rather cold month (a week of near zero):

380634

[Pat Barry]

Pat, this house has all kinds of unconventional thinking. The dead air space is inside 3 1/2" of polyiso foam, and serves two purposes. One a disconnect between the outside insulation and a path for wiring so that the outside envelope does not have to be compromised except where boxes are routed in. It allows 2" of foam behind boxes. Also the air currents do not make any difference as each individual section is sealed and so the and so air is not taking a part through the wall cavity but rather just moving around.

I have been doing dead air space ceilings for years with a sealed layer of 1/2" polyiso HD, 3/4" strips, all caulked in and then drywall. The results have been amazing and no problems with trapped moisture. This is the first time I have done it on walls, but this is an experimental house, so why not experiment? I have to admit the wiring issue was the catalyst but I am curious by nature. I have probes installed in the wall that allow me to keep track of the temp and humidity of the air in the airspace in the wall.

If no one tries anything new, nothing changes.............
I agree that experimentation is often the best way to confirm a new idea. On the other hand, there is quite a lot of published data related to insulation. A quick search yielded this for example ( http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/Rvalue.html). This shows the R value of 3.5" of air as only R=1, contrast that with the R10/13/15 you can get by filling that same space with fiberglass insulation and you can see the dead air is not energy efficient. On the other hand, you have valid reasons for wanting the air spaces, such as for wiring, maybe sound deadening, etc and you may already have enough R value with your construction methods. The problem is coming up with data for your situation. I hope it works out well for you and your customer.

[Tom M King]

We built a 1600 sf low tech, passive solar house in 1980. In 2007, we added a 1312 sf addition to it to the West. The original part has decent insulation 19 & 38, but nothing special.

The addition has double 3" exterior walls, 1" polystyrene on the outside between 1" nailers for the White Oak board on board siding. I think the outter part has 13 in it, and the inner paper faced 15. There is a 1" space between the two 3" walls with three horizontal spacers fastened to each 3" section. Walls are 10 feet.

The ceilings in this part are flat. Underneath the ceiling joists is 1" foam board. The 2x8 joists have R30 in between them, and then a layer of unfaced R30 running perpindicular across the tops of those. When the inspector looked at it, he said,"You know, code only calls for an R30 minimum". I said, "I don't care what the minimum is. I'm going to insulate the hell out of it."

The floor is R30 with the thin, fanfold foam board, like is sold to go under vinyl siding fastened underneath the floor joists, mostly to hold the insulation that I laid in there when we framed the floor-never liked those wires.

I think the biggest thing I did to help is the way I did the ends of the ceiling joists, where that space communicates with the ventilated soffit. I cut plywood bulkheads to take all the space, but fitted around baffles that let the air get from the soffits into the attic space. On the inside of those baffles, I used scraps of the 1" foam board, and sprayed foam around them to completely seal the ends of that space.

My Wife wanted a heated floor in the new bathroom, so it has one, but we can't use it. If we warm the floor up enough to feel warm to the feet, the room gets up to 90 degrees.

I had put ducting in that addition to work for a 2 ton heat pump, that HVAC contractors figured we needed for the addition. That's the size we've had forever in the original part.

I never thought that it would take that big of a unit, so we decided to live with it for a while, and see how it did.

Long story short, it never needed any additional heating or cooling, other than what it got from the original part. I ended up tying the return ducts together, and even though the ducting is now way oversized for the old 2 ton unit, it works just fine.

We built another 440 sf kitchen out the North side the same way. Still didn't need to add any more heat or cooling. We're in the process of building a 1068 sf gym on the East end, that will balance out the first addition to the West. We may put a mini-split in there, but we're going to use it first, to see how it goes.

Last month was the coldest since we've had the additions, if I'm remembering correctly. We have subpanels off of subpanels to the barn and shops, all off the home panel. There are two heated 16 gallon horse waterers, a couple of chicken waterer heaters, a heated bed for the outside cat, heat lamps in the hen house, a heater in the room in a shop where all the paint, and finishing supplies are kept, small refrigerator and water heater in the barn,boats, tractors, mower, and anything that has a battery but doesn't get used over the Winter much has a Battery Tender on it, and a couple of miles of 9 ga. aluminum hot wire along the top of the horse fencing, and probably something else that I forgot. Our electricity bill last month was a few dollars over 200. That's the first time it's ever been over 200, or even fairly close to it.

I never calculated anything. I just insulated the hell out of it.

[Tom Bender]

It honestly doesn't sound all that efficient. It sounds like any old house anywhere for the most part. You don't mention the square footage or actual cost to heat and cool the building for example, or draw any comparisons to what you deem as typical utility bills for your area. You don't mention what temperature you heat / cool to. Lots of missing info to make any conclusions from in my mind. Assuming you are correct though, what do you think is giving the biggest savings in your utility bills?

It is any old house. The keys are to not include the wasteful options;

No sliding glass doors

No fireplace

No tall ceilings

No skylights

It is also critical to have good windows and doors properly installed.

Gas forced air heat burns about $600 in gas per year. 1300 sq ft plus full basement. 68 degrees at night, 72 in the daytime.

As an HVASC salesman / engineer long ago, I made load calculations for a number of buildings. The heating loads from largest to smallest are usually;

1. infiltration

2. window and door transmission

3. ceiling transmission

4. wall transmission

so spend your money and effort at the top of the list.

[Larry Edgerton]

I agree with your list with an exception on tall ceilings. I would agree that you are indeed heating more space, but the typical hot air at the ceiling, cold at the floor can be pretty much mitigated by paying very close attention to rule #1. If cold air can not come in and settle at the bottom pushing warm air to the top temperature differential is very minimal.

I will use my current house as an example. My main room, 26'x32' has 11' ceilings yet the temp differential between the floor and ceiling is always around 2 degrees. This is a copy of a schoolhouse that I owned in the seventies, and I can tell you that the temp differential on that place was about thirty. No hard facts but the loft was almost unbearable, and your feet were always frozen when on the floor. I always loved that place so I built a copy, but super efficient.

I studied Canadian methods of conserving heat years ago as an efficient home is good for repeat customers. They were doing pressure tests long before we started using them here. Another good source is Joseph Listbureks "Building in Northern Climates".

I use some of his principals in my houses, and have added some of my own. The "Thermos Bottle" ceiling I incorporate was an experiment on my own house that worked out amazingly well for example.

I bought a trashed after divorce house that needed a lot of work, but did not want to tear down the old ceiling because of the old rock wool in the attic, so I retaped the drywall, added 3/4" furring strips, then drywalled again, making sure that all electrical boxes were sealed. There was 5" of rockwool above, tops of the ceiling joists were still showing, and yet I could heat the house and hot water for under $100 in the coldest months, and I am above the 45th parallel.

In my current house I used the same principal but as it was new construction my first layer was 1/2' HD polyiso foam as is used under EDM roofing, sealed, furring strips crossing the trusses, all caulked in so if one section is compromised it would not affect the adjoining space, and again, all electrical outlets sealed, then 5/8" drywall. Some areas have wood ceilings, but there is a finished drywall layer under the wood.

This house, 1340 feet with 26 large glass windows/doors and 11'ceilings in about 2/3 can be heated for under $100 a month in the cold months. If I was not a claustrophobic and had a lot less windows it would be substantially less, but that is a price I am willing to pay. I now have a wood furnace in the basement with gas as supplimental and heat the house on 8-9 face cord a year I cut off of the property.

[Ole Anderson]

I built my house in MI in 1975 and thought I was being efficient by sheathing the exterior in 1" foam, then standard r-13 walls with 6" in the attic with vinyl windows. Code is so much better now. Last year I helped my son re-side a flip house with vinyl. In order to pass inspection, we had to completely wrap the house with Tyvek and tape it to the window and door frames to seal against leaks. Something I wish had existed 43 years ago. I have since added new aluminum clad wood windows and an additional 8" of cellulose insulation in my attic as well as insulating the garage and adding insulated doors there (I keep it at 42 degrees in the winter with a small unit heater). Also added a bunch of ridge and soffit vents and a 95% condensing furnace. House is still not very tight. I did have to have a fireplace though. Always shut the damper the morning after having a fire. I just totaled my gas bill for the last 12 months, it was about $550, not complaining. 1530 sf ranch with a walk-out basement.

[Nike Nihiser]

"dead air space", sounds good in theory, very hard to execute and keep that way.

[Art Mann]

I don't think there is a single best solution for everywhere. One has to calculate the cost/benefit ratio for the weather and political climate. I pay 1/3 to 1/4 the price of electricity as California. It is the same as solar power. A practical system for CA would never come close to breaking even where I live.

[Stephen Tashiro]

Matt, I don't disagree, but with closed cell spray foam, you can balance the lower material cost of 2x4 walls with the higher initial cost of the insulation and end up better than you would have with 2x6 and conventional insulation...

Ignoring energy efficiency (!), what the best insulation from the point of view of tearing into a wall to fix or modify wiring and plumbing? My only experience along those lines is tearing into walls that have ancient paper insulation that looks nasty and disintegrates when disturbed. I imagine foam to be something harder to get out of the way yet leaving "cleaner" debris.

There are YouTube videos criticising Great Stuff "Fireblock" foam as being easily ignited. Is the type of foam used to insulate whole houses less or more of a fire hazard than other types of insulations?

[Jim Becker]

Stephen, I know that the closed cell foam used in our addition has a fire retardant in it and it's even ok that it's exposed in the attic area which is conditioned space within the envelop. But it's absolutely true that doing retroactive wiring and other things is pretty darn hard with spray foam in the wall, especially if the bays are filled. You can't just "fish" something. For anything beyond just a couple of feet, the best way would be to cut a channel in the drywall to gain access to the full extent of the wiring to be added, cut out a channel in the wall for the wire, do the installation and replace the strips of drywall with the required tape/mud, etc. Alternatively, pre-installing conduit can be helpful for some "anticipated" changes/additions. Unlike cellulose with a binder blown into walls and smoothed before covering (or other similar materials) closed cell foam is very rigid. Open cell foam is less so and closer to the cellulose with binder filler, but still not fun to retrofit through without fully exposing it. Honestly, fishing through fiberglas bats under drywall isn't a piece of cake either!

[Tom Bender]

So again, spend your money and effort at the top of the list. 2x4 or 2x6, fiberglass or foam, not going to make a measurable difference. Infiltration is number one.