OFG, those links never contained answers. A couple of years ago, we generated a list of questions to be added to the FAQ. Answers from members of the forum were to be submitted to OrchidDude, the Keeper of the FAQ. There were only a couple of us who submitted any answers. I recused myself from those two, based on the fact that 1) I built my GH from a kit, and 2) I was quite vocal that winter in our annual vented/unvented heater debate and I didn't think I could be viewed as objective. Now would be a good time to ask for answers to those and any other GH FAQ questions that you might have. Submit Q&A to OD. SB

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

I'm short on time today but I didn't want everyone to think I had bailed. I'll work from the most recent post back. Rhome is correct. The squares are 2x2 so the dishwashers are 2 ft, the fridge and freezer are 30" each, the sink area is 48" but I will probably use a 36" farm sink. Microwave placement has yet to be decided, since this is a very preliminary drawing but I was thinking in the island. I have concentrated the items that will get the most use...range, fridge and sink at one end of the kitchen, so that there is no need to go round and round the island, or at least that was the idea, other than an occasional trip to the freezer, which in our current house is in the basement, so I don't think I will mind a few steps. Our current kitchen is 12'6"x14 and excluding the prep sink and the fridge (which we don't have in this kitchen) is almost the exact same setup. Our current island is 7' and the work area is concentrated on one side. I located the fridge in this area so that anyone coming in for just a drink would not get too much in the way. Kelbrad, thanks for the link. I will check it out later this evening, along with researching what other options are out there. ChapNC. I am working in excel, using a graph paper template that is 2'x2'. When I drew the bathroom I had a shower on that outside wall, but then thought that a tub would be a better idea for a guest room. However, I failed to lenghten the room to accommodate a tub. Thanks for pointing this out, as I had missed it. meldy nva. I will look at the kitchen again. I'd prefer the laundry near the kitchen, as that is where I spend the most time and makes switching out a load or folding more convenient. The master is large, but as mentioned above, we do have several pieces of furniture. We could definitely make do with smaller. Do you have ideas on how to rework that end of the plan and still access the guest bedroom? I would love to see your ideas. Rhome410, I really like your kitchen layout. It is similar to what I have drawn and I am happy to hear that it works for you and your family. It gives me hope that mine will work someday too. Okay back to work now. I will try to address the rest later.

Are you under a firm deadline, other than convenience in not living with and in a work site any longer than necessary? Are you OK with setting up a minimalist kitchen function for the duration? (keep and move old fridge to another room, get some hotplates or portable induction cookers - at least one maybe two, MW, biggish toaster oven, rice cooker and washing your dishes in a PR sink - using a counter made of plywood on sawhorses?) Could you get through the holidays with such a set-up? It really depends on your tolerance for camping out in your own house and how frustrating you will find juggling children and tradesman (many of the same management/coping skills apply, but don't try shoving a pacifier at the electrician). Whatever time frame you come up with, imagine how it would be if it took exactly twice as long. Would that throw larger family plans into a tailspin? Because that very well may come to pass. Still, GCing one project, and your own at that where your won't have trouble communicating your ideas because they will all be in your own brain, seems like it is possible. Are your kids and DH the flexible, roll-with-it types? Or does change destabilize them? What does your Mama think? My own Mother GC'd the building of her house when she was in her 60's. I know I spent a lot of time on the phone with her as she vented about the days' progress (or lack thereof). I thought it was great that she did it, but I think if I had had doubts my doubts would have discouraged her and made it harder. Also, get several more bids before you give up. The Official Kitchen Industry is awash in price gouging in some places because it is an emotional purchase, dealing with aspirations, expensive equipment most people only buy occasionally and mysterious systems (water, electricty and drains), etc. Also, try breaking it apart into sequential episodes to see if you can make it work that way. HTH L.