Cellulose Insul gave me 20% savings from last year

Savings Calc Methodology Questions for 1924 house

Been waiting for the latest gas bill. Luckily the average temp was the same 53 degrees for both periods mid Oct to mid Nov. I took the following efficiency measures:

1. In March I had cellulose blown in to the 4" between sheathing and walls.

2. End of Nov '05 I had the fireplace flue capped. (So savings from that was realized for only half the period.)

3. This heating season I lowered the supply temp to 160 from 180.

4. Did about 20ft of caulk sealing in attached sunroom on slab. Some basement bandjoists filled with fiberglass.

In this period I used 64 therms (2.21 a day) compared to 80 therms, (2.76 a day). Thermostat settings are weekdays 65 6am-8am and 7-10pm; weekends 65 7am-10pm. Setback temp for other times is 62 this year and 60 last year. (very little effect since it was so warm night heat rarely came on.)

This is a 210K gas-fired WM atmospheric installed 1982 (165DOE and 143Net) with a 40K loss and 80K gain, 2 floors cast iron and basement Slantfin 15.

I think I may also have saved an additional 5% or more between 2004-05 by removing 4 complete wooden rad covers and 2 partial metal covers (top only 'trays').

My question is, if the comparative temps were not the same, how would I calc in the average monthly temp differential. Or is the average daily temp for the period a true basis for savings calcs? Better to use degree days?

Thanks,

David

Some more main steps

1. Adding 3/4" tongue in groove styrofoam under new vinyl siding. That's next month. Should also better weatherseal doors. Windows are vinyl replacement double-pane from 20 yrs ago, still in pretty good shape. Someday insulate spaces where old metal weights hung.

2. Put polyicinine foam under attic eaves and on gable walls. I'm going with a non-vented attic. (Westchester, NY).

3. Remove direct hwh and install direct to existing boiler. hoepfully next month.

4. Someday when I can do major piping job to correct series piping rad to rad, I'll also add a mod/con boiler, re-insulate basement.

I'm happy with 25% savings from all I mentioned but I guess your experience tells you it could be more. With the 3/4 styrofoam and all the other things I'm guessing it could go to 50-60%.

Things had to be done when they had to be done so yeah tough to isolate each factor. But hereon in I should be able to get a read on the styrofoam, indirect, then the attic insulation, the last one separately.

Whether I go by avg. outside temp or degree days, how do you calc vs usage? If there are 100 degree days one month from 06 and 200 same period in 05 and your therms are X (or outside temp is 50 one month and 40 the next) what's the formula? Just divide degree days (or avg temp) by therms or vice versa?

Also my electric went down 12% for that month. Since my gas bills have been over $2200 a year, savings is welcome.

Thanks,

David

I agree with JP

that degree days are the best indicator. Are the savings you cite in dollars or therms? Therms are the only real benchmark as you can imagine. Bottom line number for conversation is "Therms per Degree Day" so it will be comparable year to year.

Our gas bill shows the total degree-days for the billing period (usually one month). We divide the therms shown on the bill by the degree-days shown on the bill. Actually we use the average July/August monthly consumption as a baseline (usage due to hot water, drying, cooking etc) and subtract that from the monthly winter therms.

If your bill doesn't have degree-day information, wunderground.com has a 'History' function. Our gas company also shows degree-days in a web table, updated daily.

Of course, in all cases these ddays are for a major airport in the area rather than specifically for your house.

Summer DHW Usage

I would not skew your summer numbers for winter use, David. The "dirty little secret" about DHW standby losses is that they are greater in summer.

Sure there is less delta-T and the ground water is presumably warmer (this swings a bit across the seasons anyway). The average ground water temperature below frostline is about the mean temperature of your climate anyway. It cancels out overall. In late fall the ground temperature peaks, in early spring it is as cold as it gets.

But consider that in summer you do not want additional heat, it works against comfort and any AC you have going on, for what that is worth. And in winter, any losses go to heat your house.

Stick to the big picture of degree days and subtract your summer usage as a net.

My $0.02

Brad

infra red photos

Thanks for all the feedback. These infra-reds (b&w and color versions) were not done at optimum time. March 30, probably 40 degrees around 10AM but they give some idea. I watched the cellulose workers and though I'm not trained in this they seemed to stuff those cavities to bursting. I also made sure they opened additional clapboards in areas where firestops prevented full access.

Attic: currently there's some old fiberglass under attic floor, probably 4", but it's compromised in areas and some of the covering floorboards are out of place. AC handler is up there and ducts penetrate floor. We have some work to do in that regard. I notice that on cool not cold mornings, the 2nd floor --underneath attic-- will call for heat when the main floor doesn't so I'm sure we have a chimney effect going on from some (partially insulated but unsealed) basement band joists etc. A blower test done before any work was done yielded .9ACH. I'm hoping we've knocked it down to .5 or so. Will test again after all the work is done.

The plan is to put in polycinine foam under roof eaves and inside gable walls to make a non-vented attic. We have a 10ft peak in attic so it's useful as some kind of space, so we'd rather not dump cellulose on attic floor. Even with the foam I know we should seal some of the attic penetrations. I realize that the best heating efficiency might come from insulating the attic floor rather than the roof eaves etc. but we need to lower summer temps for AC handler and the 8" supply ducts that litter the floor.

I think renting a thermal camera --rather than hiring someone--would be best. Could also locate heat piping route in basement ceiling etc.

Thanks,

David

You know, JP,

those are excellent points that many, including myself overlook. It is easy to forget that November has more intense sun on vertical glass than in September and especially June/July, because it approaches at a low angle, more perpendicular to the glass.

November is "I told you so" month when owners who "value-engineered" a 4-pipe system to a 2-pipe system cry for cooling when they have been heating for a month.

Who said "November is the Cruelest Month"? Either an HVAC engineer or an owner with buyers remorse...

Based on degree days looks like 26% savings

If I'm correctly reading info at wunderground.com figures for same period are:

2005 = 437 Degree Days, 80 therms minus 14TH (nonheating) = 66Therms divide by 437DD = .151 DD per therm;

2006 = 445 DD, 64 therms minus 14TH = 50Therms/445DD = .112DD per therm. Savings of 26%. (for cellulose, fireplace seal and lower boiler temp.)

Now what if I varied my day or night indoor temps--I shouldn't for test's sake--but if I have to how would one calc additional usage? Based on X hours of comparative higher room temp?

Thanks, that's really a great site.

David

assumptions

david, without 'seeing' your house, I made some assumption:

1.) the original windows have no insulation between the window frame and the framing opening of the house.

you can insulate this perimeter by remove all sides of inside window trim, or depending on the orignal outside trim, take the outside trim off around the windows and insulate from there. since you are moving the windows outward, i'd guess you will redo outside window trim.

i use slow expanding foam, 3/4 of pocket. biggest point is to do reduce any air leaks with the expanding foam.

but i agree, doing this from inside is better, but if the inside trim was in great shape, then you do not want to mess with it.

I'm suggesting, when the foamboard is installed on old siding, leave a nice gap around the windows 3/4", then go back and 'foam-in' this gap for a better seal.


sometimes 'ventless' attics will greatly reduce roof life do to roofs inability to cool down. seems thats what curls shingles on southern exposures. also can lead to ice dams