How efficient is your house?

[huisjen]

There's a way to figure this out. I've seen a few people here lately complaining that their houses are cold and their bills are high, and they don't know what to do or think.

There are two sides to this: How bad is your heating equipment (efficiency and cost of that particular fuel), and how leaky is the house (both excess air flow and lack of insulation). Either way, the first thing to do is get a rough figure of how much heat you go through.

The hotter you keep the house and the colder your climate, the more heat you'll need, all other things being equal. If you go to this site: http://www.degreedays.net/ , you can find a local airport to get weather data from, put in what temperature you keep your house at, and ask for the last 12 months of data, or whatever you have heating fuel records for. It will come in a weird file, but Excel will open it. Yes, you have to not be afraid of spreadsheets. Just add up all the numbers for the period in question. These are heating degree days. The more of them you have, the colder your climate is. For instance, Tehachapi CA has about 4700 a year, with the house kept at 65° (which really means 68°, because the lights and fridge and bodies do the last 3°) Here in Maine, the number is more like 7000 per year, give or take.

Next, figure out how many BTUs you're using. We're talking about "off the truck", rather than after the inefficiency of whatever heating equipment you use. Try this: http://hrt.msu.edu/Energy/Notebook/p...or_by_USDA.pdf The bottom of the first page gives heat values of some common fuels. Multiply the number of units by the heat value to get your total BTUs. Look elsewhere for the firewood values though. Good hardwood can be 26 million BTU per cord, and light softwood or poplar can be around 13 million.

Then figure out your living area in square feet. Don't include unfinished basement area.

Okay: Divide the BTUs by the square feet, and then divide that by heating degree days. You should end up with a number between 3 and 25. If you fall outside that range, I'll be amazed. Numbers below 5 are good. Numbers above 6 usually mean there's work to be done. Numbers in the 7-10 range are common for my clients as starting numbers, and up to 12 isn't uncommon.

I know all that seemed like a pill, but it's not much worse than sixth grade math. If in doubt, find a sixth grader and tell them it's a science project. Once you have a number, post it here. People will want to know where they stand compared to the rest of the crowd.

After that, we can talk about what to do about it. There are other considerations, like how much your fuel costs per BTU, and how efficient your equipment is, but this is a good basic triage number for how efficient your house is.

[Becka03]

I am going to reply to this so I can have my 17 yr old do the math for me lol... and if I dont reply I willl forget the thread! Thanks for this post

[Danaus29]

Sorry but I'm not letting your site download files onto my computer.

I did check the closest airports heating degree days (default 65*F) and came up with only 448.

Ok, Wunderground got me all messed up. Found AEP's site

1.6 and I included the basement because we usually keep it heated.

[MushCreek]

It should be interesting to see how my new house performs. I used a computer program for calculating heat loss and gain, which factors in not only the ICF construction I used, but windows, floors, walls, doors, number of occupants, etc., etc. In our SC climate, the heat gain in the summer is only 9,000 BTU, and the heat loss in winter is about 12,000 BTU. With such a small load, central A/C is out of the question, so I'm using ductless mini-splits rated at 26 SEER. Time will tell.

[Randy Rooster]

MushCreek - I was looking into icf construction before opting for traditional stick built with 2 x 6 walls- I really wanted to do it, but it is so new in this area I didnt want to be the guinea pig. I am wondering what your experiences have been with it.

[mistletoad]

6. Now what?

[simi-steading]

Interesting, but for the rest of my life, I won't be worrying about it... My gas is free, cutting and splitting wood is good for me physically, and I can keep my home heated for free, and I keep it a lot hotter than I do when I'm paying for heat...

OH.. during the summer is no worry either.. open the doors, and turn on the fans... No A/C... I'm good with that... so much nicer letting in the fresh air..

[MushCreek]

I don't yet know how the ICF will perform, but I like what I've experienced so far. Very strong, quiet, straight. I considered well-detailed 2X6 framing, but, working alone, I had no way to stand up the walls. ICF blocks are featherweight, and go together like Lego's. I did hire an experienced ICF contractor to pour the concrete, though.

A big benefit is how air-tight the walls are. I only had to detail the few penetrations. Turns out, though that a house has 6 'walls', not 4, and I'm finding out right now how hard it is to detail the attic and basement.

Simi- I hope your health allows you to process firewood for the rest of your life. At age 60, I'm starting to see my limitations when it comes to physical labor. Not bad yet, but I can see the outcome.

[simi-steading]

I keep thinking and worrying about that MushCreek... . I'm lucky though, both sides of my family, most live to 100 or real close..

My grand father is 92 now and he still gets on his bicycle and rides 10-15 miles several times a week... I just keep hoping I got all their genes..

[Harry Chickpea]

Although the calculations would work well for many, we have enough variables to throw them out of kilter. We use heat-pump some days, and on colder days use propane, but we buy propane on a pre-pay so usage can only be generalized. Since we also use it for cooking, but not heating water, it gets more complicated if we process vegetables or such. We also use space heaters on cold nights, which is resistance heat, and electronics has a base load as well. Our water also varies in temperature according to season, but we wash more clothes in the heat of summer.

Right now I'm trying to trace a "phantom" loading of about 10kwh/day that I cannot account for by tracking with a Kill-a-watt meter, the utility meter, and amp induction coil. A buck a day is $365 over a year.

[highlands]

Very interesting math.

For our cottage:

Our degree days are 7,254.

I know that I use less than 0.75 cord of dry (mostly deadwood) hardwood from our land which according to the MSU.edu site is about 11MBTUs.

252 sq-ft of house no basement

Efficiency: 11MBTU/252sqft/7254 = 6.2

The thing we need to improve is more insulation on our roof and window shutters or something as they are where we lose heat. However, it isn't a priority because we're already burning so little wood that it is just a small fire in the morning which is nice to dry things with. Even without heat our house doesn't freeze because it has high thermal mass (100,000 lbs in 252 sq-ft masonry inside insulating envelope) and decent passive solar gain - we're on the east side of the mountain so it is not huge. This is in northern Vermont central mountains USDA Zone 3.


Now, here's the numbers for our butcher shop:

Same 7,254 degree days

Zero heating

About 1,400 sq-ft and about 1.6 Million pounds of thermal mass inside an insulating envelope.

Efficiency number: 0BTU/1400/7254 = 0

Our butcher shop is extremely massive and we want it to be at the temperature range that it naturally floats at (different sections are designed to float at different temperatures). I designed it to do this naturally. It is capable of operating without electricity if I'm willing to forgo deep freezing as currently setup. For our product refrigeration we will initially have a freezer compressor so there will be energy use there.

Time will tell what the cooling energy number will be like after I've had a year or two of data to look at.

I have designed the butcher shop so that down the road we can use coolth tanks in the attic to store winter over the the summer months so we won't need that power. The coolth attic will be the single biggest energy improvement we'll be able to do. I have a few smaller ones planned too.

Cheers,

-Walter Jeffries
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
http://SugarMtnFarm.com/

[littlebitfarm]

Tried it for my house.

HDD= 6463

I go through about 400 gallons of propane a year, that is heating, cooking, and hot water. So I took 100 gallons off for non heating. So 300 gallons of propane = 21300000 BTU's

House is 1350 sq ft

I came up with efficiency of 2.44!

I was living in the shed next to the house as it was being built. Every night I came over with caulk or spray foam. Roughly 1/3 of the house is backed up into the hill so dirt is 4' up the sidewalls and those walls are 2 separate 2 X 4 walls, so 8" thick.

Windows are double pane with storm windows.

I have had the crawlspace walls on the exposed sides spray foamed. The attic has 12" of fiberglass and another 18" of cellulose blown on top of fiberglass.

Guess my efforts have paid off!!

[Use Less]

Relevant asides: 1) interior humidity level has a lot to so with how comfortable given temperatures feel. 2) how long odors linger in your house gives you a sense of the air turn-over. The faster that burnt onion smell gets gone (without venting), the faster teh air trades out, taking your heat with it.

[highlands]

I just realized something that isn't accounted for in this math. Air exchanges. We do a lot of air exchange so that our interior air is very fresh which is better for our health than letting the air get stale. We basically have a incoming free flowing 4" diameter pipe to provide fresh air. I would not want to be breathing stale air. Since we only use three quarters cord of wood a year in our cold northern climate I'm not too worried about that last little bit.

[woodsy]

I got a 2.5

Passive solar home, wood heat only.
80 mil BTUs or 4 cord of mixed lower grade hardwood
1500 sq. ft.living area
7500+- heating deg.days

Think i did the math right.

[Rectifier]

I got 10.

11400 degree days, 1500 square feet. Half the house is 100 years old, the other half is 30 years old and 2x6 construction.

It's a little skewed as the records used for gas were from the previous owners:
- kept the place at like 80 degrees
- The furnace was short cycling badly and when I moved in I found the fan belt only consisted of the backing, minus the rubber part. You can imagine the efficiency of this furnace.

I plan on replacing the 1960s 100kbtu furnace (60% eff) with a pair of 40kbtu hot water tanks (80% eff) for a hydronic system, to allow easy integration of alternate energy sources, be they wood, coal, solar, or a combination.

Going to put more fiberglass in the attic, too.

[jwal10]

I can close the door to the bedroom/bath on a 10 degree night and heat this place with 2 candles with the 2 of us in here. It is 11' x 22'. No heat and us in the bedroom for the night, door closed it will be 65 degrees in the bedroom, 55 in the main room, before sunup. When the sun comes up it will start to warm on a clear 10 degree day. I start a fire in the wood cook stove for 15 minutes with some paper and 6 pieces of Douglass fir kindling from a 1"x4", 12" long, then let it go out. 3 pine cones and a 2"x4" added will keep the stove burning for an hour to heat water, we are good for 4 hours in here. The south sun comes in through the big window and heats the heat sink interior wall and floor of the air lock entry, woodstove heats this wall from the back side. On cold dark rainy days we use the wood cook stove. This morning it was 32 outside, 60 in the main room, 64 in the bedroom/bath. When the sun came out I opened the curtain on the big window and it was 68 by 9:00am. Not a cloud in the sky and 55 out now at 10:30. I didn't build a fire, ate some cottage cheese and strawberries....James

[opportunity]

HDD 9450 we use mostly willow and old rotten wood to heat the house it doesn't burn well but it is here and we have to do something with it. We have around 1000 square feet of living space but the full basement is a huge cold sink it freezes down there in the winter. I got 13 for my number we have insulated some of the walls and put insulation in the attic but we still need to replace windows and fix the basement up it makes the floor so cold. The dog door also doesn't help it lets in a lot of cold. We are better then when we moved in the last owner spent about $500 a month to heat we spend about $100

[Maura]

Before we bought our own 1,000 gallon propane tank, I asked the propane guy how our fuel consumption compared with other homes. He said for the size of our house we use less than other homes. I'm really sure we are efficient because we built the house ourselves. The living part is above the garage, so we saved money on building foundations. We also save in heating the garage because it is part of the house. We have in-floor radiant heat. The slab of the garage is kept at a lower temp than the upstairs. Radiant heat is the most comfortable heat, and I think the most cost efficient. We have also saved money by buying propane in the summer when it is at it's cheapest rather than buying it as we use it. This has been the worst winter in our 12 years we've been here, but we are still humming by on the propane we bought in the summer.