How to determine HDD's and "savings" from furnace upgrade

Last fall I upgraded my furnace from a 88,000BTU 80% to a 44,000BTU 90%. My gas bills are at record highs, although I'm sure some of it can be attributed to the record cold weather we've been having in Moore Oklahoma. I've talked to friends/neighbours/co-workers and they have said theirs have "gone up some" but won't give specifics.

Where do you find HDD data and how to you calculate the increased "load" from colder weather? I downloaded the HDD file using a 60 degree base temperature. Heat doesn't run when it's above 60 outdoors.

Views: 1015

Reply to This

Replies to This Discussion

Hi Bob,

from a link in my other thread I caught this quote:

On page 8-14

"For ease of processing and of meeting data requirements, the industry standard for many years was to use a fixed 65° F for both heating and cooling degree-day bases. However, actual and normal hourly weather data are easily available now, providing flexibility in the choice of degree-day bases.

In general, a degree-day base of 60° F for heating and of 70° F for cooling usually provide better fits than a base of 65° F."

http://www1.eere.energy.gov/wip/pdfs/53827-8.pdf

Bud

Good find, explains why 65 was always used as a "compromise" base temp. Base temp varies considerably based on solar gain/wind chill. Using average daily temp certainly makes more sense than high/low for a particular day. I'm still liking the "monthly average temp" method.

We just got our latest meter reading, 8.59DTH March 12 meter read date. Use is again consistent with weather.

Here's a reply received when I shared Bob's conundrum with a pro I contacted at the Canadian Centre for Housing Technology:

Hi Steve,

A long time ago, I worked as a housing engineering energy consultant and found out enough about Heating Degree-Days (HDD) to know they are very tricky to use, especially on a monthly basis.

There are so many other factors that affect house consumption in addition to the ones roughly captured by HDD, that you can’t trust that index for a detailed monthly analysis of heat consumption. Some of these other factors include solar gains, internal electrical gains from activity, heat gain from people, wind (though not wind-chill as some of your discussion indicates), and thermal mass as per your discussions with Marianne below. For example, HDD simply truncates data involving temperatures that are hotter than its baseline (for example 65F), so that it will over-predict heating loads on days with warmer daytime temperatures and cold nights. The mass effect carries the house through these periods in reality. The furnace can be shut-off by the owner because they know the heating season is over, but the HDD keeps adding up.

With the large amount of data we collect for our houses, we have never looked at correlations of our house consumption with degrees days. Rather, Marianne has investigated the relationships of the impacts of temperature, solar and wind on the heat loss of the CCHT houses. She also studied the impact of ground temperature on heat loss in the basement, which affects the energy balance of the house. Even with all of this, her correlations always showed scatter, indicating that we don’t yet have the whole story on how weather and surroundings affect heat loss. That is why we went to the trouble of building an identical Reference House to the Test House – the Reference House is like a very expensive weather sensor that integrates all these factors which we use to predict what goes on in the Test house for a given set of technologies and configuration. Even there, we have to benchmark the Reference house ‘weather sensor’ as it changes from season to season.

So the challenge you have taken on is a big one – we have no easy fixes to use HDD as a predictor or adjustment to your consumption data. Others in the business of analyzing customer consumption data in more detail, for example oil and gas utilities or consultants may have had more success.

Best regards,
Mike Swinton
Principal Research Officer
Research Manager
Canadian Centre for Housing Technology

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

David Eakin replied to Kaushal Bharath Raju's discussion Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.
"More food for thought on this subject - read this (fairly) recent blog by one of the most respected…"
2 hours ago
Curt Kinder commented on Christopher Morin's blog post 5 Things New Energy Efficiency HVAC Contractors Need to Know
"You left out air distribution...Without at least a passing glance at how much air moves through the…"
7 hours ago
David Eakin replied to Kaushal Bharath Raju's discussion Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.
"I mis-spoke - I was referring to the Midori House in Santa Cruz. Have an in-depth discussion with…"
13 hours ago
Profile IconScot Davidson, j jarvella and Michael joined Home Energy Pros
20 hours ago
Kaushal Bharath Raju replied to Kaushal Bharath Raju's discussion Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.
"Hi David & Bud, $400/sqf > $300 sqf. The latter is the minimum cost of new construction in…"
21 hours ago
David Eakin replied to Kaushal Bharath Raju's discussion Affordability & Deep Energy Upgrade/Passive House Retrofit in Berkeley, California.
"Kaushal, There was a deep energy retrofit upgrade project (to Passive House standards) in San Jose…"
23 hours ago
Kim Tanner updated an event

Beyond Residential Testing at The Energy Conservatory

May 14, 2014 to May 16, 2014
The Energy Conservatory (TEC) is hosting a Beyond Residential Testing event. In addition we are…See More
yesterday
Casey Gesell posted a video

Super Attic - Attic Insulation System

http://www.drenergysaver.com | 1-888-225-6260 The new Super Attic: Advanced Conversion System -- converts your attic from a vented attic into an unvented at...
yesterday

Casey Gesell just added their location.
(via Member Map)

yesterday
H.O. Electric posted a video

H.O. Services, Generator, Electrical, Plumbing, Heating, Cooling, Belmont, Lexington, Arlington, MA

H.O. Services is your residential Electric-Plumbing-Heating-Cooling Specialist. We are an electrical contracting company providing homeowners the best Electr...
yesterday
Jim Gunshinan's blog post was featured
yesterday
Luis Hernandez posted a discussion

Air Source Heat pump or mini-split efficiency

Greetings everyone!    I have a technical questions I hope I could get some feedback! I understood…See More
yesterday

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service