Replies

1. 
   David_Thomas | Jan 31, 2002 12:12am | #1

   *
   Louis: Post your house's dimensions, construction details (age, insulation, how tight - air-infultration-wise, etc), and location (city, state). I can give you a rough estimate of heating load.

   There are programs that take all the details of your house and give you heat load for different temps. I'm torn between the much greater work to do all that data entry versus the ease of using some rule-of-thumb numbers. In large part because there's not an easy way capture fit-and-finsh and other workmanship issues in the computer programs. Whereas with the rule-of-thunb appraoch, I'll use a factor of 0.35 instead of 0.30 if you tell me the workers got wasted every Friday. And a factor of 0.50 if they were drunk every day of the week :-)

   What does the boiler send hot water to? Baseboards? Radiators? Radiant floor heat?

   Repost and we can continue this discussion. -David

1. 
   Louis_Romano | Feb 01, 2002 02:25am | #2

   *David,The boiler will send hot water to baseboard and radiant panels.The house is 5 years old,2 storys.2770 square feet (which includes a 336 sq ft garage): the foot print is 32' X 40', with an additional room 10' X 15'. The walls are 2x4, with 1" of foam sheathing, tyvek, and tight board and batten siding.The ceiling is insulated to R-49.All windows are high performance, low E.poly vapor barrier throughout.Slab on grade.I built the house myself, very tight construction.Presently heated with one Fisher wood stove, the biggest one, some rooms upstairs are a little cool on the cold days, but it heats pretty easily.Located in Morgantown, WV. I believe our Temperature Rating is 4°.

1. 
   Louis_Romano | Feb 01, 2002 02:34am | #3

   *David, I sent a message but not sure if it got thru as it did not show on the message board, so here goes again.The house is in Morgantown, WVThe boiler will send hot water to baseboard radiators, and radiant panels.2770 sq ft., 2 storiesslab on grade, perimeter insluated with R-2.9walls: R-11, plus 1-inch of foam, 1/4-inch air space, tyvek, 6 mil poly vapor barrier inside, and board and batten siding.ceiling insulated to R-49.all windows high performance, with lowEtight, caulked, construction.Presently heated satisfactorily only with a large Fisher wood stove.Thanks!

1. 
   Jim_Coate | Feb 01, 2002 06:02am | #4

   *On rule-of-thumb method versus entering lots of details into some program: I have both types of estimates for the house I'm working on.The detailed estimate is a Right-J form from the Wrightsoft package when I was thinking of baseboard heat. It shows about 25% less Btuh/ft2 for the basement (12.3) than first floor (16) and about 50% less Btuh/ft2 for the second (7.2) than the first floor. The radiant estimate was completely based on the square footage so the same for each floor (22 Btuh/ft2).Is the Wrightsoft package assuming much of the heat will rise? Or based on the insulation around each level? Or just way too much detail resulting from over engineering the problem?

1. 
   The_Tennis_Court_Builder_...on_t | Feb 01, 2002 06:23am | #5

   *50 gallon hot water heater would do you fine.Btus... would be low... lower than 50K I bet.near the stream,aj5000btus continuous would take care of cold days for you most likely.

2. 
   Louis_Romano | Feb 01, 2002 04:02pm | #6

   *Jim,Maybe the software takes living comfort into account? Therefore more living done on first floor so keep a little warmer than basement. Then, with the heat rising, a little less for 2nd floor.I ran my complete dimensions through a software by Wirsbo. I came up with a total Heat-Loss of around 43K, which I thought was low. A knowledgable friend told me to go no lower than 90K on the boiler?Lou

3. 
   Louis_Romano | Feb 01, 2002 04:06pm | #7

   *aj,your off the cuff comes close to the results I got from the Wirsbo software. I have also been informed to undersize, rather than oversize the boiler.One thing of note, I talked to someone at Buderus, he said that in New Hampshire the rule of thumb is multiply sq.ft. by 35 for BTU design output (this puts me needing a unit that can put out 97K if I was in NH). This is of course based on they're design temperature of -10°. Our design temp here in WV is +4°.Lou

4. 
   The_Tennis_Court_Builder_...on_t | Feb 01, 2002 09:30pm | #8

   *Your home is twice as tight as average and has twice the insulation. That means you can have the rules of thumb. I start with 80Kbtu boilers if oil as they are the smallest and can be jetted to produce much more. Most average homes use this size. Your home is larger than average but is ultraefficient making it size more like the smallest homes I do which are half your sqft.You should be all set.near the stream,ajI wouldn't do a heat analysis myself ever. Anyone I know that does them, increases the results anyway to cover their butt.

5. 
   Louis_Romano | Feb 01, 2002 09:54pm | #9

   *aj,I'll be using Propane.Also input/output Btu's differ.80K output?

6. 
   The_Tennis_Court_Builder_...on_t | Feb 01, 2002 10:14pm | #10

   *I am talking input... as they are all rated.near the stream,ajI installed Teledyne Laars not long ago for an LP unit. It was the largest residential unit they made. Came with hotwater tank. Radiantec recommended them.near the stream,ajI say to you should use the Polaris hot water heater as both your hot water and heat. It is a high Efficiency condensing type.http://www.radiantec.com/best.htmhttp://www.ewaterheaters.net/polaris.asp

7. 
   David_Thomas | Feb 01, 2002 11:25pm | #11

   *Louis: I get 23,000 BTU/hour (net) at 0F. That would be about 30,000 BTU/hour gross rating for NG, LPG, or oil. I used a factor of 0.12 BTU/hour/square foot/degree F. And multipled it by 2770 sq ft and 70 degrees F.My rule of thumb is 0.10 for a super efficient and tight house. Your's may perform at that level. But I added a bit for the vertical walls. Everything else sounds boffo. In my own house, I planned on a factor of 0.10 and achieved 0.07 (watched the thermometers and the gas meter for a few days). But it has lots of spray urethane foam therefore very high R values and exceedingly low air leakage.So AJ is right, you could heat the sucker with a hot water heater. The 42,000 BTU/hour (gross) rated one I use would more than do it. I also use mine for domestic hot water as well. But I only need 18,000 BTU/hour at -40F in my smaller house so I have more left over for domestic hot water. With one or two adults, I'd consider a single HWH for heating and domestic HW. Larger family or ANY teenagers, and I'd use a separate HWH for domestic HW. Maybe feed it from the space-heating HWH for zippy quick recharge. -David

8. 
   Louis_Romano | Feb 02, 2002 02:32am | #12

   *So next question is a boiler or hot water tank brand.aj: I looked at the Polaris, I think it starts at 100K which seems big. Buderus smallest starts at 74Kand Teledyne has one at 50K.Also there are issues about induced draft.I want something good but cost is a factor.I guess a very small boiler is what makes you guys start thinking Hot Water tank?

9. 
   Nick_Pitz | Feb 02, 2002 04:24am | #13

   *Not to throw a wrench into the works, but since AJ, you brought up Teledyne Laars, I thought I would throw in my 2 cents, FWIW. Used to install Teledyne boilers (JV series) in our jobs, and have installed two of the Mini-therm boilers (with integral DHW tank).Over the past couple years I have decided against installing them anymore. I have had problems with the hot surface igniters, and replaced three igniters in two years. Also, both Mini-Therms were mis-wired in the control wiring from the factory, which took a lot of head-scratching to figure out after installation. Just generally not had wonderful experiences. Not trying to slander Teledyne, but just passing along my experience.

10. 
    The_Tennis_Court_Builder_...on_t | Feb 02, 2002 06:30am | #14

    *Nick...They probably fired the goof up employee by now... The minitherm integral unit I installed has worked flawlessly for 8 years or so.The ignitors are not Teledynes I bet, so I wouldn't blame Teledyne for bad ones.The Polaris will do a dandy job and is way more efficient than the other choices.near the stream,aj

11. 
    Jim_Coate | Feb 02, 2002 06:03pm | #15

    *David (or others): I'm curious what rule of thumb number you might use for a house such as what I'm building: It's a 2.5 story house over a basement that is walk-out on back so 50% of basement has stud walls.Foundation walls are studded out to add ~4" spray in insulation inside; stud walls are 2x6 with foam (?) to be sprayed in, with 1/2" ply and 3/4" foam and claps on exterior. Roof is 2x12's with "raft-r-mate" spacer things and 10" of fiberglass batts and then a layer of 3/4" foam.Generally tight, will have HRV/ERV. I'm fanatical where I can be but combination of old & new construction leaves a few weird thin spots. Anderson double-hung low-E windows, one Anderson 9' sliding door unit, 2 Velux roof windows.I think I'm in the 0.1 - 0.3 range but not sure where?

12. 
    Wet_Head_Warrior | Feb 02, 2002 06:15pm | #16

    *You size boilers this way.1. Stand across the street.2. Hold your arm straight out and starting with 1 finger slowly raise your fingers until you block the house from view with your fingers.3. Count your fingers.4. Now multiply that number by 100,000 BTUs and you got the boiler size. Forget that fancy computer stuff.kidding...

13. 
    The_Tennis_Court_Builder_...on_t | Feb 02, 2002 06:44pm | #17

    *Jim.... you forgot the one important item...Sqft!... _____________________so fill in the blank...Off hand tight small homes need 50K... 4000-5000sqft... 100K 10,000sqft 200K and 3-4 HVAC set ups.near the stream,ajFor standard construction... we use a 80-90K BTU Boiler. up to 2500sqft. It's the smallest made stock unit.

14. 
    David_Thomas | Feb 03, 2002 12:37am | #18

    *Jim: For the construction you describe in Post #15, I'd use a factor of 0.10 BTU/square foot/hour/degreeF. A touch lower but for all the openable glass. 0.10 as described.For typical construction of the last 25 years, I use 0.30.For a mixed house, multiple each factor by the square footage of each type of construction. -David

15. 
    Jim_Coate | Feb 03, 2002 06:21am | #19

    *Oops - to fill in the blank, it is just about 3000 ft2.So 3000 x 0.1 x 70 degree diff = 21K BTU/hr. You all and the computer paint a pretty consistent picture... I'm ignoring the locals who apparently went to school with Wet Head (the house is only 8' back from the road, so it does take a lot of fingers to hide it...)Looks like me & Louis are in just about the same situation, facing same decisions and all. The smallest gas boilers I know of are about 50K BTU/h (eg Burnham RV2). I'd like to use the extra to power the DHW tank... has anyone quantified how much that active family with teenagers uses, as in would I need to go to the next bigger boiler to keep the DHW happy? (No family at this time to use for data, but the house has 3-4 bedrooms so has family potential).

16. 
    Louis_Romano | Feb 04, 2002 10:34pm | #20

    *Any suggestions for radiant panel and radiant baseboard manufacturers as the prices vary greatly.For instance Buderus radiant panels appear to go for about twice what VEHA go for.Also the radiant baseboard by Burnham looks good. Any feedback on this brand.I can't decide whether to focus on radiant panels and a boiler with outdoor setback ability or just fin-tube baseboard elements and a straight up one temperature boiler. Also is there any advantage to the DHW tank add on to a boiler as it forces the boiler to work year round. Is a boiler rated at say 60 or 70K btu still more efficient to run to only heat domestic water than say a 34k standard HW tank?Lots of questions, but I feel like I'm learning alot.Thanks for the help.

17. 
    David_Thomas | Feb 04, 2002 11:20pm | #21

    *Jim: How big a HWH? I'd take my answer from all the HWH out there. 30,000 to 40,000 BTU/hour gas units provide decent recharge times. 5,000 watt (17,000 BTU/hour) electric HWHs do NOT provide a decent recharge time, IMHO.Louis: You raise an interesting question, Is it better for your boiler to keep it running or to let it "rest". I feel a car run periodically will last long than one allowed to sit for 6 months at a time. But does anyone have data on boilers?

18. 
    Louis_Romano | Feb 05, 2002 12:39am | #22

    *BTW any one have any input on the quality of a radiant baseboard by a company called Radiant Technology. It is a narrow baseboard made of aluminum that has water channels built into it. It is a true radiant element as opposed to fin tube baseboard.

19. 
    Nick_Pitz | Feb 05, 2002 01:33am | #23

    *The radiant panel baseboard made by Radiant Technology (actually, it is now made by a company called Hydronic Alternative, or something like that) is a pretty good product, with some limitations. I have installed several hundred feet of it, so I know the product well. It definitely looks good (looks like a plain 1x6 baseboard) and it heats very well. Quality of the manufacturing is good. Installation is essentially easy, but it requires some planning and knowledge of the product to get it to come out well. There are quite a few tricks to installing it to make it look nice. I am not a huge fan of their cover plates and endcaps which dress up the installation. Output is relatively low (200 Btu/ft) so you have to have the space to put enough in. Also there are limits on the length of a loop (60 ft. of panel and 120 ft. of tube) due to the small size of the tubing (3/8").

20. 
    Jim_Coate | Feb 07, 2002 01:31am | #24

    *Thanks David, aj, and all for the help... and thanks Louis for continuing to ask all the questions I'm thinking!