Well, OD, you didn't answer. May I post a polished version anyway? First, restate the subject as a question: How do I calculate the costs of running a greenhouse? Answer: The question is best answered by using an example, but first some formulas: Watts=amps*volts 1 KWH = 3,413 BTU 1500W electric heater produces 5120BTU Propane is 91,600BTU/gallon Q=deltaT*A/R Q=BTU heat requirement per hour delta T is the difference between outside temp and desired inside temp A= the surface are of the greenhouse is square feet, not including the floor; ie, the roof, side walls, and end walls R= the R value of the glazing Two important points about this last formula...some heating calculators use "heat loss value" (HLV) instead of R-value. Don't get confused, the HLV is just 1/R. The formula using heat loss value is then Q=deltaT*A*HLV. The other important point is that you use a different temperature when calculating your average energy costs over a month than you do when you you calculate what size heater you need. Heater calculations are used to determine how much heat you will need on the coldest night of the year. For this, you use your coldest winter temps, for example the colder end of your zone. For calculating heating costs you need the average temperature for the month. Here are some typical R-values for common glazings or coverings: 4 mil polyethylene 0.83; 4 mm (5/32") twinwall polycarbonate 1.43; 6 mil polyethylene 0.87; 6 mm (1/4") twinwall polycarbonate 1.54; 6 mil poly double layer (inflated) 1.43; 11 mil woven polyethylene 0.95; 3 mm (1/8") glass (single layer) 0.88; 16 mm (5/8") triplewall polycarbonate 2.5; Polycarbonate/fiberglass (single layer) 0.83 OK, let's say we are contemplating an ACF 10 x 12 Cottage Greenhouse. We first need to calculate the surface area of the greenhouse. Using the diminsions found on the website and some simple geometry, we calculate the surface area of each sidewall to be 55 sq ft, each roof side to be 64.6 sq ft, and each end wall to be 75 sq ft. Therefore the total area (A) is sq ft is (55*2)+(64.6*2)+(75*2)=389.2 sq ft. The website tells us that this GH comes in 6mm twinwall polycarbonate, so the R-value is 1.54. A quick search shows that in this particular zone 7a, the average January temperature to be 28.4 degrees. We want to keep our greenhouse at 50 degrees. So the "delta T" is 50-28.4=21.6 degrees. Now we can calculate the BTU per hour necessary to heat the greenhouse in January. Q=deltaT*A/R. Substituting the numbers, Q=389.2*21.6/1.54=5459 BTU. To figure daily use, multiply by 24 hours to get 131016 BTU/day. To figure monthly use, multiply again by 30 (days in the month) to get 3,930,480 BTU/month. Now, lets say we heat with propane. Knowing the BTU in a gallon of propane, we can take our BTU/month and divide by the number of BTU in a gallon of propane. 3,930,480/91,600BTU/gal propane to get 42.9 gallons of propane we would expect to burn in January. We just bought propane at $1.69/gal, so this would mean my January cost would be 42.6*$1.69=$72.52/month. Let's say we heat with electric. Take the same BTU value and instead of dividing by the BTU/gallon of propane, divide by BTU/KWH. 3,930,480/3413BTU per KWH=1151KWH. If my energy cost is 7.169cents/KWH, then heating electric should cost about $82.52 for the month of January. OK, well, our hypothetical DW says that the winter costs are too high and she cannot be convinced to go ahead with the greenhouse. Let's look at what we can do to lower the winter costs. Let's insulate the north wall...no sun comes through this wall, and if we insulate it with foil-backed polyisocyanurate 1" board, which has an R-value of 7.04, we raise the R-value of the north wall to 1.54+7.04=8.58. We can recalculate Q using the same formula, but adding together the BTU lost through the north wall and the BTU lost through the rest of the greenhouse. The formula would be Q=(deltaT*A/R)+(deltaT*A/R). Our greenhouse is oriented north-south, so the north wall is an end wall with a square footage of 55 sq ft. Our BTU formula changes: Q = (334.2*21.6/1.54) + (55*21.6/8.58) = 4826 BTU/hour This equals a monthly use of 3,474,720 BTU, equal to about $72.99/month heating electric. What else could we do? Well, we could add some thermal mass. Let's put 8 black 55 gallon drums in the greenhouse. One BTU is defined as the amount of heat required to raise one pound of water one degree F. The water will warm during the day and release this heat at night. One chap we know has measured the temperatures of his water at dawn and at dusk. The temp is 74F at dusk and 66F in the morning, a drop of 8F. Eight 55 gallon drums hold 440 gallons of water which is 3520 pounds of water. A 1F drop in the water temp releases 3520 BTU. An 8F drop releases 28120 BTU overnight. Over the course of a month, this is 844,800 BTU. Therefore, the total monthly BTU could hypothetically drop further to 3,474,720-844,800=2,629,920 BTU. This is 770.55KWH heating electric. At $0.07169/KWH, this is $55.24 for the month of January. Our calculations assume 100% efficiency. Some heaters, particularly vented heaters, are not 100% efficient. If you know the efficiency of your heater, you can adjust the calculations accordingly! Now on to summer costs. The greenhouse in the example will need an exhaust fan and HAF fans. First the exhaust fan. The greenhouse is 900 cubic feet in volume. Therefore, we need an exhaust fan that is rated at least 900 cfm. A 16" exhaust fan at Charley's is rated at 1095 cfm. The website tells me it draws 1.8 amps. Remember that watts=amps*volts. So when it is on, the fan uses 1.8*120=216 watts. If this fan runs 16 hours per day in the summer, it will use 216*16=3.456KWH/day. This is 103.68KWH/month, which, at the same price of energy we have been using above, amounts to $7.43/month for the exhaust fan. Let's say we use two 8" long life HAF fans. This may be overkill for a greenhouse of this size, but you will get the idea. Each fan draws 0.6 amps, and at 120V, this is 72 watts. Running 24 hours a day, each fan uses 1.728KWH/day, or 51.84KWH/month. Total use with the two fans is again 103.68KWH/month or $7.43/month. Know the usage pattern and amperage draw of each electrical appliance in the greenhouse allows us to calculate the cost of running each item. OD, I cleaned it up a little and also reinsterted the line breaks in the formulas. Thanks. SB

The bid that was most off for us came from the architect's building partner. The architect was present at that meeting and was visibly embarrassed by the builder's lack of knowledge about the plan. He had obviously not studied it in any detail before the meeting. Our blueprint was meticulous and very specific... and they actually argued in front of us about their own creative differences. That was a real turnoff. It's hard to get apples to apples when people you should be able to trust are promising you anything, preparing to give you the cheapest alternative once you've signed their bottom line. The only way to avoid this crud is to educate yourself beforehand. We knew our foundation would run over 100K... it was the nature of the beast. We were quoted 20K by one builder. Another quoted 60K. Builder A had no crew that built on steep slopes so he just guessed. Builder B was going to use the same concrete guy that Builder C ended up using because he was essentially the only guy in the area anyone trusted with our engineered foundation. So there' s a big difference in a 60K bid and a 120K bid, and it has more to do with builder C making Slick (that's his name) actually sit down and study the freaking blueprint. Our lead carpenter came to the new house with a new blueprint for the future manse down the street. He was sweating bullets over it because those people want an estimate for their custom woodwork. Our builder got the job based on what he was doing on our house, but this house will really push the envelope as it is a trilevel foundation with about 6000 square feet. I have to respect the care and attention he gave that blueprint. He already knows every inch of trim in that house. Still, I know they will make their best estimate for costs- with as little guesswork as possible. I just didn't see all builders themselves as "apples to apples". Some are really lazy about doing their homework or assume they will talk you into cheaper options later on so they can get close to their underbid. There are a ton of things a client has to be aware of... EDUCATE yourself on all aspects of your project so you are not fresh meat to some of these arrogant so and so's.

Thanks. I just checked the Smithfield site, it's supposed to be removed from wrapper, wrapped in foil and warmed in 325 oven for 10-12 min/lb (so about 1 hr for this ham). Then the glaze packet is supposed to be brushed on while it sets. I was going to add some b. vinegar to the brown sugar glaze but I think I'll just see how the ham tastes without it, maybe I'll offer glaze in a gravy boat? Not a baked-on glaze so it doesn't matter, and that way we can taste if it goes with the wine. My mom specified the ham - I've never cooked one, though I do pork loin all the time. We're not really big on cured/processed meats in this house though the guys do like low-salt deli turkey for sandwiches. DS will eat ham but not ham sandwiches. I thought the price was high ($4/lb) but after going to the Smithfield site and seeing what they charge, I *really* don't want to mess this up!

I second what live wire oak says. Glazing is an art. I had glaze over white done in the existing/tweaked cabinets in our last house and it was just magnificant, the man was an artisan. I saw many of his samples before hiring him, and he did a finish sample before we went forward. I interviewed others too and there was SUCH a difference. Here, we were going to do the same thing. I interviewed one so far and he sounded so good I asked him to do a sample. It was pitiful. His idea of glaze didn't even look like glaze it just looked like someone had used a foam brush to apply a little tint. The glaze he left in the cracks around the raised panel looked like they had forgotten to apply the paint there! Also, the finish of the paint was ripply. Just a night and day difference. I would not go forward on anything like this without a full door sample. You may have to pay for the sample but it's well worth it. Was going to pay the last man to come out but it was so expensive we could get new cabinets, which I think we may just do. The jury is still out on that.