Energy use after new windows, HVAC
I have a small bungalow (1400sq ft) built in the late 20’s. It has 15 windows down, 8 up. No insulation in the external walls except one kitchen wall. About 4″ of rock wool in the attic. The attic is not vented. Full stone basement. No major moisture issues.
Over the last year I have replaced 9 of the 36×54 windows with Andersen Woodwrights with low-e coated glass. I have also replaced a circa 1980 60% efficiency furnace and similar AC with a new Lennox 95% dual stage furnace and AC.
I was expecting to start seeing some change in energy use. As far as I can tell, we’re now using more energy. It’s possible I suppose that this past winter and now summer were colder, and hotter, than the year before. However, I’ve been watching our bills and comparing with last year and so far I’m not seeing much change, and most months we’re using more.
My question is this: Is it possible that something about our house envelope has changed due to the tighter windows that is causing some other phenomenon? More loss through the upstairs, or less escape for super heated attic air, or…??? The attic does get ridiculously hot and radiates down into the living space. I would like to address that as well.
Thanks for any thoughts or advice.
chris
Replies
Been there, done it!!!
You might not have as high of a heat loss threw the window now that you have replaced them.
Keep in mind the windows are a small part of the package.
Seal air infiltration and insulate!!!!!!
No matter how effecent of heat source, you are still heating and cooling the outdoors, but now you are doing that with a more effecent furnace.
I would start with the attic and work down.
Heat loss and gain is *mostly* through the ceiling/roof.
Air seal all those little holes that go up into the attic space - wire holes in the wall plates, chimney chases, plumbing chases, gaps at the wall ceiling.
Then blow an R40 to R50 worth of cellulose insulation into the attic. Don't bother removing what is there already. Don't waste time on fiberglass insulation.
Your heating bills will drop a bunch. And so will your cooling bills.
Air sealing and attic insulation have the biggest bang-for-your buck in saving energy dollar$.
New windows have much less impact on energy bills compared to attic insulation.
After the attic, get some insulation (blown dense-pack cellulose) into those walls.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Thanks for the quick replies. I knew going in that I probably wouldn't see huge changes just based on the windows, though our old windows were pretty leaky. (you could feel wind blowing through them on windy days)However, I thought I'd see a change, all things being the same, from before. If I didn't change anything else, and replaced windows and put in new HVAC, why would energy consumption go up? Maybe it's all in my head, or lower/higher temps, or maybe we've cranked up the thermostat setting as we've gotten older. :) I will say that we THINK the house feels more even throughout.I know the attic is our biggest weakness now. The house temp rises all day during the summer because of radiant heat. I've actually done reasonable sealing of air gaps, so the heat loss during winter isn't as bad as you'd think. In other words, our house is not the first on the block to melt snow off the roof.I know we need better insulation up there, but I'm not sure how to proceed. We still have some knob and tube wiring active up there, and it's a walk-in attic that we use for storage. Any suggestions? I'm thinking I need to replace the wiring first, then remove the rock wool and replace with cellulose, but we need to be able to walk around and put down plywood flooring, etc. Would it work to add spray-in foam to the roof?
Adding spray foam to the roof underside would then bring the attic into your conditioned space. Spray foam isn't as DIY as blowing cellulose. But it can be done if you do the research.If you do not do the spray foam, the knob and tube has to go first. Build a 20 inch platform to store all your stuff. Then you can add cellulose under the platform. Leave the old insulation up there, pile the cells on top of it.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
An older ballon framed house I renovated once......1st thing I did was to blow in some cellullose insulation. Very good and really killed outside road noise. Then replaced windows 1 at a time, (andersens).
The insulation was blown in so good it stayed in place went I had to open up the wall for the windows. Some entire walls I removed the plaster & lath, insulation stayed in place.
Got to go, it's a cool rainy day, I am off the the attic to seal & insulate.
Have fun!
your energy sampling is too small to make a judgement on
take it as a given that you have improved your energy use by replacing your windows.. but your other losses dwarf the window loss
you are on the right track... now you have to address the gross lossesMike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Hi,
You can run this simple heat loss calculator for your house, and it will give you some idea where the major heat losses are. It should also give you some idea what you should save in energy with the window replacements:
http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm
Some of the inputs, like air infiltration, are not easy to estimate, but it should still give you some idea.
You can get a rough idea of severity of winter/summer by comparing hating and cooling degree days:
http://www.weatherdatadepot.com/
Fuel suppliers usually keep track of this to know when people are likely to need a fill up, so you might try an local home heating oil or propane seller to see if they have degree day numbers if link above does not have a station near you. Heating load is more or less in direct proportion to heating degree days.
Seems like you should work on the insulation.
Might be worthwhile pulling aside the attic insulation, and sealing up all the wire/plumbing/light fixtures penetrations, then blowing in a lot of cellulose -- this should be ease and not too expensive?
The "Insulate and Weatherize" book by Harley is a good one for developing a plan of action.
Might also try and energy audit with blower door test -- this will give you and idea of infiltration losses, which may be a large part of your problem?
Gary
I'll give my 2 cents ... it can be a complex interaction of pieces of the puzzle that give you your results. Some that come to mind: The installer didn't seal the windows or made some install error that affected air leakage. Something else changed that you haven't revealed ... e.g. oh and by the way we installed 15 recessed cans in our new kitchen remodel.
How about lifestyle changes? Family grow bigger? Smaller? Maybe w/ the new cool stuff you actually set the stat higher? Job change keeping you at home more or less? New interests/activities that have affected your use of the house? New thermostat working OK? You do use e.g. night setback, right?
On the weather side ... it can be very profound ... varying as much as +/-25% year to year ... that could be 50% in extreme cases. So check the HDD and CDD for your area for the same months as the bills you are looking at. Do you have more years of energy use records? The more years the better. If you are a spreadsheet geek like me ... you start entering that stuff in and graphing it out ... compare it. That will tell you the story.
Also double check the meters. Read them. Do a reality check. Everything look OK. Are you only looking at cost or the consumption? It sounds like you are focused on the consumption (that's good).
As an experienced energy sleuth, I dig for this kind of stuff to determine if you are simply perceiving things wrong or if things are in fact ... wrong.
The suggestions you've received about air sealing the envelope are a good idea no matter what else is wrong, but your Q about why your energy bills seem to be higher after new windows and furnace are still not explained.
You may be a victim of the "bigger is better" mentality of many HVAC contractors when it comes to HVAC equipment sizing.
It's possible that your new furnace is creating greater pressure imbalances throughout the house.
This happens when supplies and returns are not balanced in individual spaces. The more powerful the blower, the worse the imbalances. So, a new, more powerful furnace blower may be causing more severe imbalances. And since the house envelope is leaky, the imbalances are costing you.
For example, if the master bedroom has inadequate return, anytime the door is closed, the room will become pressurized and conditioned air will leak out. Equally, some other part of the house will become DE-pressurized as more return air is taken from this space to offset the supply-side loss in the MB. This de-pressurized part will leak air INTO the house.
Without seeing your particular house, I would still guess that the return air is inadequate from certain rooms. This can be tested easily.
With the furnace blower running on high speed ("cooling" speed is usually high speed), close the door of the room, and feel for airflow under the door. Do this on both sides of the door. If you feel air coming at you, you know the space on the other side of the door is pressurized, and your side is de-pressurized.
Besides this possible energy loss, your new furnace, if it has a more powerful blower, will also be causing greater air leakage anyplace where unsealed ducts run in an unconditioned space, like attic or crawlspace.
Good stuff here guys - thanks for all of your replies.Here is some additional info:The ducts are all in the basement and sealed with RCD#6 mastic. Not being an HVAC contractor I guess I can't swear that I wasn't taken advantage of, but I used a reputable company and was told that our old system was oversized for our house. Supposedly we were sold a smaller unit. That said, I'm certain the blower is more powerful and so we could be seeing some air return issues as pointed out. It's a 1927 airplane bungalow with one large return in the dining room floor and another smaller one in the hallway floor. I'm installing the windows myself and am meticulous about it. I'm confident that they are installed tightly, so long as the windows are doing their jobs.I have an electrician coming this week to bid on replacing the last of our knob and tube so I can do some additional attic work.Thanks again.chris
I have a electrican friend that claims he can reduce electric use by balancing the loads in the panel. I know this is true but to what extent. Perhaps experts will chime in on this one.
My electrican will monitor electric use on each leg of the panel and move breaker to balance.
I have a electrican friend that claims he can reduce electric use by balancing the loads in the panel. I know this is true but to what extent.
Huh???? You KNOW this is true?
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
It's like I said, "claims" but I have heared that a balance load across the legs in the service panel opperates more efficently. Make sence, one side not pulling working against the other.
Maybe Hartman will have some words of wisdom.
But this guy was from the 60's and consumed lots of wacky tobacky!! ?????
Balancing the legs is good practice in design and installation, but does not affect efficiency. I think in three phase power distribution, code allows a maximum % deviation, but I'm not sure
Hey! I bit!!
I NEVER inhaled, though :)
Given that you've checked/confirmed some technical details ... what about the family/lifestyle? Someone move in? Occupying the house more often (e.g. after retirement)? Buy new gadgets? Heating more rooms? Stat turned up higher/lower?
Assuming that you KNOW that your bills went up and it wasn't due to weather, You need to dig a little more. If you haven't confirmed the weather part of the equation, you should do so.
No major lifestyle changes. I don't remember how we had our old system's thermostat programmed now, so it's possible that our new program is a degree or two warmer/cooler. I still need to check out temps from last year versus this year. Here in the midwest this has been an unusually mild Summer, which is why I was surprised that we were using more. I'll have to check out one of those weather pattern sites.
If meters are being used, make sure you are looking at actual meter readings and not estimated readings.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Definately a nice thought on the HVAC! Something to check.
You are comparing kwh and therms, right? Not just the amount of the bill?
You basically describe the exact house that we had - and just finished adding 3800 SF to,. finishing in 2008. Our monthly energy costs are up about 150% even though we more than tripled the size of the house, unadjusted for energy cost increases by the utility in the last several years (substantial).
- closed cell foam insulation (except FG in attic)
- attic ventilation (flow-through)
- Marvin Low E Argon II windows
- Weil-McClain Ultra boiler/passive domestic water
- combination radiant heat/perimeter hydronic
- 15-16 SEER A/C (American Standard/Trane)
- CFLs wherever possible
- super efficient DW and washer/dryer
It all adds up in terms of energy savings