MN Renovator 2012 Hypothetical new house

[Drake]

Earth berming was a popular direction in the 70's for energy conservation. I know people that built them. The fact that they are not still popular say a lot about their practicality. Two of the three have constant ongoing drainage problem and all three have humidity and possible mold issues(in MN). They are quiet and blend with the landscape. One even has a sod roof. But they need way more space and are more expensive per sq' that super insulated or passive design. I had planned to build one but didn't. People left the sod house concept behind for a reason.

I also don't see air/air HX as very effective in our cold winters. I think hydronic heat would be a better choice which gives you several choices on how to heat the water. Of the many "green" energy concepts that I have followed since the 70's I'm looking at the one that are still working out. Like passive solar(thermal mass), hydronic heat, super insulation, space conservation, indoor pollution control, EF appliances/lighting, PV generation, SDHW(location dependent), DIY knowledge/skills. Seen many great ideas flash, consuming peoples valuable money with no return possibly even threatening their very health(molds, raydon, contaminated water.

[AC_Hacker]

Originally Posted by Drake

Earth berming was a popular...Two of the three have constant ongoing drainage problem and all three have humidity and possible mold issues...People left the sod house concept behind for a reason.

You have pointed out the potential problems with berming, but the problems can be overcome. I have a friend who lives in a bermed passive solar house, which is tucked into the side of a hill here in rainy Oregon. Proper drainage and damp-proofing was designed into the structure from the beginning. The house is dry and cozy and requires very little additional heat in the winter, and no A/C in the winter. So don't be too quick to toss the baby out with the bathwater.

Originally Posted by Drake

Of the many "green" energy concepts that I have followed since the 70's I'm looking at the one that are still working out. Like passive solar(thermal mass), hydronic heat, super insulation, space conservation, indoor pollution control, EF appliances/lighting, PV generation, SDHW(location dependent), DIY knowledge/skills. Seen many great ideas flash, consuming peoples valuable money with no return possibly even threatening their very health(molds, raydon, contaminated water.

There sure was a lot of activity in the 70's regarding energy efficiency, and a lot of good books written on the subject. I always keep an eye out when I'm in a used book store for 70's alternative energy books... I have amassed a fairly substantial vintage DIY alt-energy library.

But Drake, you are right, some of the ideas stood the test of time much better...

My Dad used to say it's much easier to have 20-20 vision when you're seeing things in the rear view mirror.

-AC

[MN Renovator]

I don't see the issues with berming being that great considering that the house I live in is undergrade without any issues. It seems that as long as you build it with the same considerations as you would with having that bermed area being a basement, I'm not seeing the issue. I see houses all the time with walkout basements in the back of a house where the front of the house is flush with the ground or maybe a step or two above. That sort of house is effectively bermed. Of course the correct solar exposure is fairly critical. In the case of a house that I know of where the owner discussed energy bills, he says that the summer air conditioning is far higher than the winter heating due to almost all of the glass being on the south.

The more that I reading about passive house building and using glass to assist with heat in the winter, whether it is double pane, triple pane, or has a pile of films(won't name the brand name) the more than I'm leaning to having very little glazing when I build a new house. In the house I'm living now, I have the drapes shut pretty much all the time because the solar exposure is terrible in the winter because the big picture windows are not south facing enough for them to get much sun at all during the winter months. My house has about 4 square feet of southern glass and it's about the only glass that brings in a decent amount of light other than the skylight. The skylight is a nightmare though, when I moved in, it had drywall and sheathing and is directly exposed the attic and had water vapor streaks from shower humidity. In the winter this kind of glass lets out all your heat and in the summer it turns my bathroom into an oven. I have little use for the light considering that if its at night I have a single 430 lumen directional LED that does the job using 8 watts. I'm putting serious consideration into having that skylight removed when this house needs to have its roof replaced. It'll free up space for solar PV panels.

So basically my house is setup so that way in the winter I get little heat from the windows and in the summer my house is baking. I had the idea of installing a removable external sheet of polycarbonate plastic or acrylic and putting Gila film on it to block light in the summer but I found out how expensive those sheets were for the massive size of the picture bay window space(three windows). I think what I'll do instead is buy two patio door screens and fashion those into a removable frame to block light and add privacy. The faux wood blinds by Levolor that the previous owners installed are terrible, don't buy from that company or go with wood blinds, these things suck in the heat and reflect next to nothing. I've hit them with an IR scanner in the summer and had them at 110 degrees in a few spots with an indoor temperature at 74 with the a/c going. They are terrible and will be replaced with honeycomb cell shades in no color other than white.

My goal is to get the a/c heat load down to 1.5 tons, I currently have a 2 ton air conditioner and on a design temp day it will run continuously(as it should) and maintain a few degrees above the set point. On a cooler day I usually operate it so it will run in a single period without shutting it off so I can remove as much humidity as possible to make a higher temperature much more tolerable and its working well. The sun-facing windows with bugscreen over the outside should hopefully reduce the load below 1.5 tons and when I replace my equipment I can confidently ask for a 40k furnace and a 1.5 ton a/c.

The reason why I'm talking about my current house is because I can see all the mistakes of this one to avoid with the next one. It seems that even though I've got limited solar exposure I can manage to get my biggest winter heating bill down to $70($60 when subtracting fixed connection fees) in winter 2010/2011 and under $45 or $35 without fixed connection fees 50 therms Jan 2012 and 180 therms for the past 12 months. These are the highest bills for a house 2200sq ft. Granted I need to disclaim that I don't keep my house at 75 in the winter, I allow it to get as cold as I am comfortable living in, same goes for summer. It's too big for my uses but when I bought it, I was buying a house that fit the neighborhood that I want to live in. Happens to be this is a neighborhood mostly with families and not very many singles or couples so the idea was to buy a house that I could sell later on down the line. A future house would likely be in a college campus area where houses that are built under 1000sq ft for one or two people or maybe 2 people and a kid(I'm talking about the average demands of a family, not what I'd live in with 3 or 4 people). I'm willing to live in a small place even if it were a family of 4 but I won't build for a family of 4 when I'm single.

Back to the topic of glazing, I'm not seeing the advantages as far as cost/benefit goes when going beyond either a really good double pane with the appropriate air gap or triple pane windows with almost all of them on the south side of the house and keeping them sized small and using a fairly substantial amount of cellulose and of course appropriate air sealing. Going completely passive seems to have lost it favor for me after seeing a Duluth, MN project get denied the passivhaus standard because they couldn't make the .6 ach50 but were very close. That house is passive though even though it didn't meet the standard. My goal is to lose the $10.50 connection fee with the natural gas provider or whatever that fee is and having heating costs be under $126 in electricity with a combination of a 9k BTU/hr heat pump and resistance heat for when we get below 0f and that thing can't produce, or in case the heat pump decides to fail. I'm still sticking to my 5k BTU/hr design load goal at -20f. The actual heat design temp where I live is between -12 and -15f depending on where I check but I'm not far from an area north that seems to be -18f. With insulating to a 5k BTU/hr heat load at -20f I'm not seeing much reason to rely on the sun for heating and it seems to be a better plan for me to consider keeping the sun out during the summer. It seems passivhaus designed use an earth tube and a condenser to do the job. Earth tubes are expensive and it seems that more and more of the project I read about are not doing this. Instead of going completely passive, I'll skip some of the more expensive steps and goals of building the status and going with what works on my terms. Things like the ASHRAE ACH for a house are IMHO way too high. I've done the math, if my house was communicating that many air changes, I'd be frozen out of my house for how much heat I'm putting into it but I have a hard time believing that a little breathing, humidity, and human sweat are as terrible as people make them out to be. IMHO controlling humidity to prevent mold is a much bigger concern that any ventilation system in my area will only require much more air conditioning in the summer to pull the humidity back down so the dew point is below 50f to make the basement safe.

[AC_Hacker]

Originally Posted by MN Renovator

Things like the ASHRAE ACH for a house are IMHO way too high. I've done the math, if my house was communicating that many air changes, I'd be frozen out of my house for how much heat I'm putting into it but I have a hard time believing that a little breathing, humidity, and human sweat are as terrible as people make them out to be.

If I'm not mistaken, the ASHRAE standard for homes has been adjusted downward.

You might want to check that out...

-AC

[MN Renovator]

The latest version of ASHRAE's manual that specifies ventilation or required infiltration prior to adding mechanical ventilation shows .35ACH prior to adding mechanical ventilation.

Personally, I'm on board with 15CFM for person. I think doing a bulk air exchange of that amount over the period of time during the day that is most favorable to the indoor temperature. Not to code, probably not officially recommended but anyone but I'd prefer it.

[RobertSmalls]

I've sketched out a few hypothetical houses myself. Maybe I'll make one of them into reality in a few years.

I was explaining the "tiny house" concept to a co-worker, and he told me about all the time he spends on his sailboat. In a boat, as in a tiny house, it's more about cubic feet than square feet. By utilizing the full height of a kitchen, having tall bookshelves (with electronics on the middle shelves, perhaps), and having a sleeping loft instead of a bedroom, you can get a lot more value out of each square foot. I see too many houses where there is nothing of utility on the top half of each floor. With a good floorplan and some efficient furniture, I wouldn't have a use for more than about 400ft².

The front yard is strictly for curb appeal. I'd place the house close to the street, and keep the small front yard looking good. There would be room for a few fruit trees in the front yard. I wonder how well a blueberry hedge would work. The street would be on the north side of the house, so that most of my windows would look out on the garden.

For me, the challenge is building a house that's far more efficient than a conventional house, but making it look very ordinary. The house has to look good from the street, and I'll have to make it look bigger than it is. Landscaping can help, as would 12" thick walls. I'd also use an attached garage to my advantage.

I want at least a two car garage, but I don't want two thirds of the front of the house to be garage doors. I like the idea of having the garage doors on the side of the house. I could add a large window with nice curtains to the side of the garage, to make it look like the house is bigger than it really is. This works especially well if I were to go with a "double deep" 2x2 car garage/lab. The garage would have concrete + epoxy floors, 2x4 construction with insulation behind OSB instead of drywall to keep costs and mantainence down. I would install an ordinary 45000BTU/hr furnace in the garage, to heat it quickly on demand. Maybe the south wall would be solar collectors for the house and DHW.

You should do the math on how much energy you use in the house vs. the car, and let us know how long a commute could get before cancelling out the savings.

I've always wondered, what drives recommendations for >R50 in the attic? Would it be different if you had a good heat-rejecting roof, such as one made of shiny metal, painted white, or covered in solar collectors?

[MN Renovator]

I always thought the idea of more insulation in the roof came from the vented aspect of the roof increasing the surface heat conductivity of the insulation since there is air flow directly over it requiring more insulation while the walls are sheated and essentially have a layer over them. In the winter with the ceiling having the hottest air that supposedly you'd want more insulation there. Not to mention it's easy to load a whole bunch of loose fill cellulose up there. In my case it's about the only place I can add cellulose to my current house without tearing out drywall, which makes it a large and easy retrofit opportunity. As long as all air sealing opportunities aren't missed before loading a pile of treated paper up there, it's about one of the only options for adding R-value for most. In a new house R60 might be more than enough, depends upon the standards for energy use that someone is going after, I'll have to read those sections of my Manual J again and read the factors on heat loss through the attic versus the walls so I can make comments about what ASHRAE thinks.

[Drake]

I didn't intend to slander earth sheltering only point out it is being done and that detail to moisture control is very important, not inexpensive and doesn't fit every location. Humid summer areas challenge the design. Some of the best performing ones today are built with PWF lumber or ICF's.

[JRMichler]

Humidity control is necessary in any well insulated house located in a humid climate. We learned this when we built our house in 2002. When the outside temperature rose into the 80's or 90's and the dew point into the 70's, the inside temperature would stay in the low 70's and the inside turned into a swamp. We had a choice - get a dehumidifier or turn on the heat. We got the dehumidifier.

Above grade or below makes no difference - it's the indoor relative humidity. Mold happens when indoor relative humidity gets over 60%.

[MN Renovator]

Your air conditioner is a dehumidifier. In Minnesota we got dew points well above the indoor temperature but as long as the air conditioner was used to bring the house down to a reasonable temperature, the humidity was plenty low. I managed to pull humidity down to 25% during the hottest weeks of the year and most weeks I'd have it in the low to mid 30's. If I let it get warmer, aka less use of the air conditioner I would have humidity in the 40's. I aimed to keep the dew point of the house below 50 degrees.

The success of an air conditioner dehumidifying your house is dependent on long cycle times, which becomes difficult when an HVAC contractor oversizes the A/C. If the blower speed is too high and the coil isn't cold enough to dehumidify the air, you have the same problem. Also if you don't have a well sealed house, you are letting humidity in, which seems to be the most likely scenario for you if you are having this problem but it is probably a combination of those issues.

The issue with dehumidifiers is that they essentially are an air conditioner with both the indoor and outdoor components inside, they leave you with a net gain of heat while drawing off moisture to a catch bucket or a drain. I made the mistake last year after reading on the hvac-talk forums that dehumidifiers were more efficient at removing humidity so I monitored my humidity and kept it at 40% but the dehum. never shut off to keep it there and burned 400watts to no end. The house was warm but the humidity level kept it comfortable enough. I ended up with the highest electric bill. I dehumidified my house using the air conditioner the following month when it was hotter and my electric bill was actually lower.

In the summer if you have issues with your humidity being that high, you should try letting the house get a little bit warm and try running your air conditioner in one cycle 4-8 hours long and tell me what happens to your humidity level. Running a long cycle will keep the a/c running its most efficient and remove the most humidity. These 30 minute cycles that some people have get rid of very little humidity.

This summer I'll be trying to use a 10.7 EER(energy star) 5k BTU/hr window A/C which is a higher EER than my current air conditioner's SEER(1986 unit) and will be in my bedroom where I want the most comfort, mostly for sleeping. If it can't keep up cooling the whole house, I will close the bedroom door and when it is overcooling the bedroom I'll open the door. If needed I'll cycle the furnace blower for a bit to suck the air around or use a few of my box fans. I got a good knack for working the 23k whole house unit last year to keep the humidity down and expect this unit if setup and used properly will do better and be cheaper.