1903 home, first time with central air, lots of questions about insulating, ductwork, etc
Hello! Grab a cup of coffee and hopefully you will have a little insight on this! Thank you!!!!!!!!!!!!!!
I have an early 1900s 2 story victorian home 2200 sq ft, currently getting a new roof next month, and had to remove the old insulation on the attic floor that was outdated in roof preparation (in april). Blown in insulation was added to all exterior walls, as well as a thin sheet of foam fiberglass insulation, prior to installing vinyl siding over the wood siding about 25 years ago. Also storm windows to cover the old windows.
The master bedroom runs about 5 degrees warmer than the rest of the house (yet its in the shade). I can bandaid the issue by using two fans (one by the bathroom register, and one in the bedroom doorway) and blowing the air from the adjacent bathroom into the bedroom (making the difference only 3 degrees). In April, the HVAC company that installed our new 96% 100kbtu furnace and 16 seer 3.5 ton w/ 4 ton coil central air is going to come back and enlarge the ductwork in the basement only, and reduce the number of turns which should help some. They said I did a good job of closing a few returns downstairs and dialing back some of the downstairs registers (all from dampers in the basement). Basically the summer mode. I was told in winter to do the reverse, close the upstairs returns, and reopen the downstairs returns and vents. No ducts in the attic. And ducts in basement are not insulated, or mastic/sealed.
We paid around 7100 for the system that included everything, even an ionizer for air quality at no charge.(and if you think these ionizers are a joke, like I originally did, there has been a huge improvement in air quality, as one person that lives here smokes and its virtually undetectable! Our nest 3rd gen thermostat schedule is set to 67 degrees from 6pm until 8am then it sets to 69. Fan always on. I do have a small dehumidifier in the basement running constantly and it drains to the same floor drain as the hvac. Humidity level in the house is not great. It is constantly between 55 and 63% (last summer with two large portable dehums running w/ window units it would be in the 70’s). I attribute this to various super tiny leaks in our roof (which is getting replaced), old single pane windows with 25 y/o storm windows, air leaks in general in the house, but also our brick foundation.
I had them also install an aprilaire 600 whole home humidifier because the relative humidity was dropping down to 10-15 percent in the winter certain days, so that to me would definitely validate air leaks. I have sealed up quite a few windows and doors since hvac installation, but its still hard to fix everything without going broke or overboard.
So the other question is….who knows how long I will live here. After the attic is sealed (the attic floor is tongue and groove with no insulation below it, but has knob and tube wiring beneath the floor in some areas. There is a layer of this reflective material on the floor almost like silver bubble wrap that was beneath these 4 inch thick 2’x5′ panels that were stacked 4-10 panels high in most places. How would I air seal a floor like mine? When the audit person said to make sure to seal the attic I thought she meant just seal the area where the roof meets the floor since its a balloon type of frame) and insulated (along with basement rim joists and vapor barrier crawl spaces, at 1200-1400 ea), new roof installed (18k), and the humidity is still running high, do I buy a whole home dehumidifier that can be controlled by Nest, for around 2-3k? Or do I spend that much or more on trying to seal up every single brick basement wall section that has bad tuckpointing when this process is notorious for not working well, and replace windows that are perfectly functional? According to a building inspector our foundation was fine and very little settling, but for sealing purposes, it would be beneficial to fix.
On the bright side of things, our budget billing has already decreased by $50, and we are already ahead this month. $240 a month. Used to have a 140k btu furnace from the 90’s and a 25k btu 220v window unit ac downstairs, and a 12k and 10k window units upstairs.
Is it normal for our AC to be running about 12-15 hours a day when its really hot out? It is lots of long run cycles so I know that is good, right? (Especially with the high humidity 90 degree days, it has ran as much as 18 hours) Also for this nest thermostat (and yes I posted this at /r/nest), there should be an option for the cool to dry feature to make adjustments. “While away: Cool to Dry will only cool to 75°F or 5°F below your target temperature, whichever is higher. While Home: Cool to Dry will turn on the AC if humidity levels rise above 70% and your cooling isn’t already on.” I think 70% is really high, but should be adjustable to at least 65. Also I have read that with newer systems its not a problem, but using airwave (a feature that keeps the fan running in its high speed for a few minutes when ac shuts off to take the extra coolness left in the coils) can cause humidity spikes due to residual water in the coil area, is this true? I have tried both settings, and made no difference in relative humidity.
I have also noticed my RH level in the basement at 60, even with the little dehumidifier, that I see quite a bit of condensation on my ductwork. Its not damaging anything, or making puddles on the floor, but it is somewhat worrisome.
Thankfully I have 2 return ducts upstairs, and plan to enlarge the basement connections to help out. One return (id say maybe 8×10″) upstairs is on the floor at the top of the open staircase in the main hallway. The other is 8×10 but the ductwork is about half that size. Its located in a walk in closet, on the floor, but the door has slots on the top half. Do you guys think making any changes to the ductwork for the 2 upstairs returns, in the basement portion only, would make a difference? I wish I had some returns higher up towards the ceiling.
I have looked into aeroseal, was quoted around $2200 to help seal up our ductwork and weatherstrip or seal any other problem areas. The company was actually really smart and was able to get our nest connected to the aprilaire using the switch I had purchased off amazon (the actual hvac installers were unable to get this working, and nest reimbursed the full bill of $350 within 2 weeks). If everyone did say this was a good idea I would totally get a blower door test done and do this as part of all the insulation and such because I will get a small rebate depending on how much sealing and insulating is attained.
Bottom line, I want to make energy efficient changes that have a fairly fast rate of return, but if its going to increase my home value, or attract buyers in the future, I am ok with it. I know one thing, buyers asking avg budget billing prices on a home where I live, the fact that I am below $250 a month is a lot better sounding than what it used to be! (even considering a small solar panel setup).
A new development has arisen. We have to have two trees cut down (3.5k) that do shade our house quite a bit. But they are so old they pose a potential future hazard as our neighbors and I are both getting new roofs. I really worry about that master bedroom because now it wont have any shade at all.
I did have an energy audit done in January. Priority 1 was insulate the attic with r50 value or better which we will do. Priority 2 was insulate the rim joists and vapor barrier the crawl spaces. I have sealed up all of our doors with weather stripping. And also even used some caulking and foam in places by doors/windows/etc.
I do not like that in our front room, there is a large 15×15 grate on the side of our staircase downstsairs that was enclosed by plywwood, which behid that on the floor is the same size return air vent. Its all open beneath this double staircase staircase and while you can feel quite a bit of air going through, isn’t that just making the system work harder? There is also no way of closing this, for some reason they forgot to put a damper on the basement ductwork for this return….but I would be scared majorly if all I had going were the two tiny returns upstairs!
And while I think our system is nice especially for the price, don’t you think a hvac company would be more concerned with existing ducts, as far as optimizing/re-configuring goes? Or is that common for a place to just come in and only replace the main components? Part of me is almost wishing I would have went with a heat pump, or even spent an extra 6k to make the upstairs its own zone with each systems returns cross connected.
And yes, the contractor did a manual J. He said that normally he would have done a smaller system, but since the energy audit person suggested 90k btu furnace, and their company didnt make one, he went with 100k. And He also would have went with a 3 ton unit with 3 ton coil, but instead did 3.5 ton higher seer with 4 ton coil. He is planning on using a flow monitor for the master bedroom before and after any changes. I still think in this case 2 stage cooling system would have been the wiser option for dehumidifcation.
Here are links to photos of my system in the basement, as well as some areas with condensation.
https://goo.gl/photos/zwXzYsNP1DE72qvo6
https://goo.gl/photos/o9rMuf8XWHZtHm2P9
https://goo.gl/photos/fmbNNQRb1EeVE9Ew9
https://goo.gl/photos/ZVXaBnRM21Uqr69n7
https://goo.gl/photos/2XCg4YsNQCynWqux8
As you can see I also moved my former gas water heater, and replaced with electric to beside the furnace. I did this because the new furnace was venting out the side of the home and it was pointless to keep our chimney that is not in perfect condition just for a hot water heater. They are going to bring the chimney down just below the roof line and place an insulated cap on top of it. In the even any future owners would like to use the fireplace they can add a small pipe out the roof from the interior chimney cap.
Thanks in advance. Sorry if I rambled on areas that are not appropriate for this forum, and any questions that you cannot answer, if you could direct me to the right place, it would be greatly appreciated!
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Replies
John,
You have written a novel -- more: you have written Moby Dick -- and I never made it all the way through. No one else is likely to make it all the way through, either.
Here's a hint: If you have a specific question, give just enough of a description to ask that question. Then wait for an answer. Later, you can tackle Question #2 and Question #3.
I read as far as the first question, and then I quit. (The question was, "How would I air seal a floor like mine?")
In the paragraphs I read before I hit the first question, I noticed two anomalies.
One, you are running the furnace fan for 24 hours a day. This wastes energy and is not recommended.
Two, you have installed a humidifier. This is never a good idea. Use of a humidifier is associated with sheathing rot. Fortunately, you apparently understand the need for air sealing.
So, I'll tackle your question.
Q. "How would I air seal a floor like mine?"
A. Here are the steps: Remove the attic floor boards carefully, and stack them on one side of the attic. (You may or may not want to re-install them later.) Hire an electrician to remove the knob-and-tube wiring, and replace it with code-compliant electrical cable.
Then follow the advice in this article: Air Sealing an Attic.
You can start a new Q&A thread if you have a second question. Next time, try to stick to 6 or 7 sentences.
First, where is this house located?
What are your 1% and 99% outside design temps? (http://articles.extension.org/sites/default/files/7.%20Outdoor_Design_Conditions_508.pdf )
A 100K (or even a 90K) furnace is more than 2x oversized for most 2200' houses, even at 99% outside design temp of 0F. Sadly, HVAC contractor implemented Manual-Js are usually junk- this looks like one of those. With the low thermal mass of hot air furnaces it won't affect the efficiency much, but a way-oversized furnace delivers a significant hit to comfort. An oversizing factor of 1.4x is sufficient to cover the coldest day of the century. Since you already have it in place, you can use it to measure the actual heat load using these methods:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new
A 3.5 ton AC is going to be 2x oversized for most 2200' houses except very air-leaky houses in very high humidity locations (like the swampy gulf coast region with dew points in the high 70s F) in which case it might be only 1.5x oversized.
Poor/unbalanced duct designs will generate air handler driven room to room air temperature differences that drive excessive outdoor air infiltration, which becomes a significant latent cooling load when it's humid outside
One, you are running the furnace fan for 24 hours a day. This wastes energy and is not recommended.
Two, you have installed a humidifier. This is never a good idea. Use of a humidifier is associated with sheathing rot. Fortunately, you apparently understand the need for air sealing.
So, I'll tackle your question.
Q. "How would I air seal a floor like mine?"
Firstly, sorry my post was too long for your liking.
Second, my furnace fan costs $6 a month to run continously and the upstairs gets hot without it for obvious reasons, and the reverse is same for cold weather.
I cannot even imagine how much work that would involve removing the wiring. It's not a code violation to insulate above the floor since it's open air beneath the planks.
Is insulating above the floor going to be a waste of time and money? We are talking at least another 5 grand to remove the floor and wiring. If you guys think it's absolutely critical then I guess I'd consider it. I have a full size door with steps leading to my attic. Energy audit person said to create a secondary door at the landing on the attic steps.
To the other poster, this is what the energy audit person recommended based on how old this house is. It's in the Midwest. With run times as much as 19 hours do you seriously think it's oversized?
You can't even imagine how leaky this place used to be.... Yes maybe when I have spent 17 grand on new windows which will never happen then maybe it won't leak.
Now I am panicking this is turning up to be a bigger project than I anticipated.
John,
Most furnace blowers are rated at 400 to 800 watts. Very efficient ECM blowers are rated at 100 to 200 watts, but those blowers are rare.
If your electricity costs 12 cents per kWh (a guess), then $6 a month buys you 50 kWh.
You're running your furnace fan for 720 hours per month. By your math, that means that your furnace fan only draws 69 watts. Count me a skeptic.
I'll bet that your fan draws more than 69 watts, and costs a lot more than $6 a month to run.
John,
Trying to air seal your attic above the old floor boards is challenging but possible. The trickiest area is at the attic perimeter. The challenge is to join your wall air barrier (either your exterior sheathing or your gypsum wallboard) with your attic air barrier. You have to do this in the part of your attic where access is most difficult.
At the very least, you would need to remove the floorboards at the attic perimeter and get in there with some spray foam. If you can manage that, and seal air leaks at the perimeter, the next step would be to install new plywood over the floor boards, and tape the plywood seams.
Then you could blow cellulose on top of the new plywood.
"the Midwest" ranges from US climate zone 3 to zone 7. Could you be at least a LITTLE more specific?
We don't need a street address or GPS coordinates, but a state & county or ZIP code would be enough to infer the local climate issues, outside design temperatures, specific local codes that might apply, and what insulation strategies/R-values that would still be appropriate, and what is "... going to be a waste of time and money...".
A 3.5 ton unit is almost certainly oversized for the load, unless it's generating huge additional load with air-handler driven outside air infiltration. Many such systems intentionally draw ventilation air in whenever the air handler is running- is yours one of those? If it's drawing in ventilation (or infiltration) when running, it adds a very significant latent cooling load whenever outdoor dew points are in the mid-60s F or higher.
Is the 19 hours of run-time the measured at the compressor (condenser unit), or only at the air handler? Only the duty cycle of the compressor counts in determining whether the
If you have the time & inclination, putting a data logger on the condenser blower would provide accurate & useful information on oversizing factor.
https://www.greenbuildingadvisor.com/blogs/dept/building-science/how-tell-if-your-air-conditioner-oversized
As long as the insulation is not in contact with the k & t wiring it's fine to insulate. The theoretical basis for the prohibition is that a corroded aging twisted wire connection could over heat if insulated directly and potentially cause a fire. To date the only such fires that have been documented have been in a laboratory, not in a house. Due to the lack of field evidence of it being a real problem, several states have revised codes to allow insulation in full contact with k & t wiring, as long as the wiring has been inspected and verified that it's in good shape.
my furnace fan costs 25 cents a day to run I was told. I will find out the exact wattage. Our power costs about 6-10c per kwh.. Regardless of cost, its a must with the duct work, lack of insulation, ETC, to keep the upstairs cool. Also when it is cold, its a cheaper way to bring the hot air down.
I am in zone 5, Illinois.
19 hour tun times where during 99% humidity, 110 heat index days, and that is only when the compressor is running. But avg time is less. No it does not draw in outside air. I am finding a very hard time believing that my system is very oversized considering the energy audit woman and 5 different HVAC people all had nearly identical sized systems. I opted for the one with the cheapest blower motor, and they were all taking into account windows, air leaks, old house, etc. SO i think you guys will be right, and my system could be oversized when I have all these improvements completed. Wishing I would have waited on the HVAC system and did all the weatherization and sealing and insulating first.
That is good to hear that I can seal without removing the entire floor. the 1200-1400 I was quoted included the sealing along the perimeter but now I am wondering how much better it would be with the floor removed. This was to use blown cellulose.
Why do I need plywood over my tongue and groove floors, if its already got a reflective layer of this silver bubble wrap style material? If I am going to install plywood on the whole floor I may as well remove the old floor?
I think that in this case I should get a few more insulation quotes. And really, waiting until late summer or early fall when temps are cooler. I think could handle removing the floor myself. It is just way too hot up there now, even with windows open with screens (no roof vents).
I am just trying to prioritize what is best, cost effective, faster rate of return, vs what would help the home sell faster, or entice future buyers. Heck one might argue installing a solar system would be the quickest and cheapest way to offset my utility costs?
You guys are great, again so far for the long post, everything is just so overwhelming. I think I am going to have my ducts reconfigured a bit, improve the upstairs returns, and use mastic to seal the basement ones myself on weekends.
Lets not forget this house has 51 windows not including doors!!!!!
Energy auditors (except for maybe the more professional RESNET raters) typically don't have a clue run the load numbers. HVAC contractors sometimes do, but have a huge incentive to oversize to avoid the 5AM call from the shivering & irate client. Even when using Manual-J load calculation tools, they tend toward extremely conservative (too conservative) assumptions on everything from air leakage to R-values, then up size from there., often using 99.6% or higher outside design temps, and ridiculously high indoor design temps. That's how most heating systems in Zone 5 end up being 2-3x (or more) oversized for the actual loads. See:
https://www.greenbuildingadvisor.com/blogs/dept/musings/saving-energy-manual-j-and-manual-d
Chicagoland 99% outdside design temps are a degree or three either side of 0F, with 1% design temps within a degree or two of 90F. See:
http://articles.extension.org/sites/default/files/7.%20Outdoor_Design_Conditions_508.pdf
Chicago, Meigs Field ______+3F_____ 89F
Chicago, Midway AP _______0F _____ 91F
Chicago, O'Hare AP_______ -1F_____ 88 F
Chicago CO_____________ +2______ 91 F
As much as I hate using rules of thumb in lieu of better methods...
A somewhat tightened up 2x4 two story framed house with retrofit wall insulation, storm windows and R19 in the attic will typically come in at about 15 BTU/hr per square foot of conditioned space @ 0F to maybe 20 BTU/ft-hr at the first standard deviation which would imply a likely heat load of 2200' x 15= 33,000 BTU/hr typ, but almost certainly within 2200' x 20= 44,000 BTU/hr. If it's the leakiest house in Chicago it might hit 25 BTU/ft-hr, for a heat load of 55,000 BTU/hr, but fixing the leaks would take priority over up-sizing the equipment.
Even in that worst-case load scenario the largest furnace you should be considering is 1.4x the 99% load, which would be about 75,000 BTU/hr, not 90K. In the more likely 33K load scenario you should be looking at no bigger than ~45K of furnace output (eg: 50K-in, 45K out, 90% efficiency). Anything bigger than that won't be needed until the next ice age, and only cuts into comfort. But there's no "payback" in swapping it out before it's run a reasonable lifecycle, so it its what it is. Still, if you have some wintertime gas bills with exact meter reading dates, run a fuel-use based load calculation on the house in it's current leakier, less insulated condition then report back- it's a 15 minute exercise, and worth getting a handle on, which would also allow you to measure & track the real improvements achieved by any ongoing weatherization:
https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/out-old-new
First floor cooling loads of 2 story framed houses without huge "sunset view" west facing picture windows run about a ton per 1500' of conditioned space. Top floors tend to run about a ton per 1000'. So with 1100' of first floor you're looking at about 0.73 tons of cooling, and for 1100' of second floor about 1.1 tons, for a grand total of 1.93 tons.
99% humidity is a relative number, relative to the actual air temp. At 99% fog begins to form, and the temperature at which it's foggy is called "dew point". Dew point is an expression of the absolute (rather than relative) humidity. Outdoor dew points in Chicago peak in the mid-70s in a typical summer, which is about an average dew point for gulf coast conditions (say, New Orleans or Houston.). So while your latent loads are real enough, they aren't nearly as torrid as most of the southeast, where most homes will have true cooling loads in the ton per 1000' range for the whole house. In Chicago your 1% design temp is 4-5F cooler than Houston's, and your humidity is lower, so it's really unlikely that your load would come in above 2 tons, once you've added the first 6" of fluff in the attic.
If you can remove the bubble-wrap-crap, do it, since it introduces a vapor barrier layer in your otherwise unknown stackup. It's also unlikely that the bubble wrap has been detailed as an air barrier, even if the seams are taped. It's cheaper and easier to lay down 4x8 sheets of half-inch OSB or plywood on too of the t & g planking, and if you ripped out the t & g you'd have to go with heavier and more expensive 3/4' goods for the floor decking. If the attic door will hang up on the thicker floor, cut down the bottom of the door, and install weatherstripping to limit air infiltration into the attic. Detailing plywood or OSB as an air barrier is pretty easy, and makes for a very robust solution.
Lowering utility costs with roof solar doesn't increase the comfort, nor does it reduce the peak loads (or at least not much- it reduces the cooling load a bit.) But if you're making the renovations looking solely at enhance resale value, forget about it- stop right now. If you're best bang/buck for comfort and lower operating cost the priority order is generally:
1: Air sealing- get serious about it, use window fans and/or blower doors to pressurize/depressurize a room at a time or the whole house, to find and fix every air leak you can find. The bigger air leaks are typically flue & plumbing chases, and band joists, and the foundation sill (usually more than the combined air leakage of all windows & doors combined.) Not all air leaks are equally important- priority goes to the top of the house (attic floor plane, and all flue/electric penetrations into the attic) and the bottom of house (foundation cracks, foundation sill, basement windows & doors, laundry vent penetrations, abandoned furnace or water heater flues, etc.) With 51 windows, if they're the typical Victorian era double-hungs the sash weight pulleys leak a lot, as does the window casing trim. It's worth spending $100-200 in materials and a couple of weekend days caulking all the trim, and retrofitting pulley seals onto the pulley ropes with purpose-made seals, eg: http://www.conservationmart.com/p-1007-anderson-pulley-seals-bag-25-pair.aspx?gclid=CLuW1JPxkc4CFYpahgodQGcPnQ
more: https://www.greenbuildingadvisor.com/blogs/dept/musings/getting-biggest-bang-your-air-sealing-buck
2: Insulation- Sounds like you've retrofitted the walls, but unless the walls were dense packed there are probably voids at the tops of those wall cavities to attend to after 25 years of service, especially if it's balloon framed with 20+ feet of wall cavity. (I remediated part of one 2-story balloon framed house a couple of years ago where some of the stud bays had settled more than 5 feet over 15 years- not the most competent installer there. I've seen others that looked perfect after 30 years, so it varies.) Insulating the attic is still important, but not as important as air sealing. The walls of the attic stairway need to be air tight and insulated too. If there is a door at both the top and bottom, weatherstrip both.
3: Foundation insulation: Even if you have some fluff crammed between the floor joists, uninsulated foundation losses from otherwise reasonably insulated houses usually accounts for 15-25% of the total heating fuel use. With a fielstone or 8" poured concrete foundation every square foot of uninsulated above grade foundation loses more heat from a 55F basement than the 10' of insulated 2x4 first floor wall in a 70F room above it. Current IRC code min is for R15 continuous insulation on the foundation walls. How you go about it matters, and is dependent on the foundation type & condition.
And now I discover that Ameren has changed their incentive policies. GREAT. Now they have made all of their weatherization stuff income based and we no longer qualify. Before, it included a blower door test, and took off about 1400 dollars on the attic and basement.
So now the cheapest company is going to try to negotiate with me and just skip doing the blower door test to get as close to the original estimate price as possible.