Manual J Questions

[Cr0ntab]

Hey All,

I wanted to get a manual J performed on my house so I bought a 2mo subscription for the hvac-calc software.

I put in most of my numbers as correct as I could.

For example, the first floor family room has cathedral ceilings through to the second floor for instance, wasn't sure how to account for that.

HVAC-Calc Manual J Link

The house came with the following:

Trane XL 80 - 2 stage 80 AFU TUD120R960 Furnace (Spec Sheet)
Trane XR 13 - 5 Ton 2TTR3060A1 Condenser (Spec Sheet)
ADP TE50460C245B2705AP Evaporator Coil (Spec Sheet)

The results of the manual J say that the house should only call for ~3 tons of cooling and 30k BTUH of heating.

The current system is 5 tons of cooling and 78k (1 stage heat) BTUH of heating.

My guess is that when the system was installed ~12 years ago it was done using a rule of thumb and not any manual calculations.

I took a peek in the attic and the furnace has a single 18" R4.2 flex duct return. Is that sized correctly? (seems small) Would there be any concern for freezing the coil?

I'm happy to install a larger return but I want to make sure it's worth doing first.

Given the price of a new system (I got back of the envelope quotes of ~$15k) I wanted to see how I could prolong it's use.

P.S. I'm currently learning how to do the "manual d" calculations with the software as well so I can see what ducting the system requires. That's a bit more tricky for me, but I'm learning

P.P.S. If/when the system breaks down I want to seriously look at ductless mini-splits, but that's a topic for a new thread.

 

[Dana]

The 18" return duct isn't super-small for a 5 ton AC or 95KBTU furnace. (The TUD120R960 puts out 95K at high fire, 65K at low fire.)

A heat load of 30,000 BTU/hr @ Corona's 99% outside design temp of 34F would super-high for a typical 2500' house. How big is this place? (That's roughly the heat load of my 2400' + 1600' conditioned basement 1920s antique at +15F.)

A 3 ton cooling load would also be on the high side for typical mid-sized houses too, unless the ducts were UNinsulated (instead of R4.2) in the attic above the attic insulation.

Most newbies to load calculations (and even many HVAC pros) err to the conservative side on all assumptions, resulting in numbers more than 1.5x the actual loads. The Manual instructions are to be aggressive, taking every possible reasonable factor into account that would lower the load. If you have some wintertime gas bills for periods that consistently stayed below 65F (below 55F would be better) it's possible to take the fuel use per heating degree day data to measure the heat load.

Similarly, on an afternon when it's in the mid-90s (Corona's 1% design temp is 96F) it's possible to measure the cooling load based on the duty cycle of the AC. An energy consulting company in the Atlanta GA region plotted the square feet per ton of cooling ratio against house size over many Manual-J's performed on client homes (most of which were in the southeast, with a high latent load, unlike Corona's negative latent loads), which looks like this:

Very few houses were under a ton per 1000', the middle of the cluster for homes under 4000' is about a ton per 1300- 1400'.

At that ratio a 3 ton cooling load would mean a 4000' house- is that your house?

 

[Sponsor]

 

[Cr0ntab]

Hey Dana,

Thanks for all the information, per usual! (I owe you an Amazon gift card or something!)

Good catch on the furnace BTUs, I read the wrong line.

I updated the calculator for the design temperatures you listed. I couldn't find Corona in the application so I just chose a close region. Using your new numbers definitely changed the results some.

HVAC-Calc Manual J

2.2k BTU drop for heat gain
1.9k BTU drop for heat loss
Cooling tonnage also went down to 2.5, which is now twice what is installed haha

The home is 2023 sqft.

Here is a different breakdown that lists the heating and cooling loads by size:

Updated Heat Gain By Component

The windows were all properly measured so I have pretty high confidence in that.
Walls I fudged just a little bit, but not a whole lot.

Updated Heat Loss By Component

I've never had a blower door test conducted on the home, so infiltration is just based off of the calculator.
The windows were all properly measured so I have pretty high confidence in that.
Walls and floors I fudged just a little bit, but not a whole lot.

I'm going to see if I can make a plan of my home tonight, at least one of the floors to help illustrate all of this. In doing so I'll re-check my measurements.

I never knew there was so much science to HVAC and buildings, this is actually incredibly interesting to me. I'm a Software Engineer by day but all this HVAC stuff has me up at night just for fun haha

 

[Dana]

The infiltration losses are on the high side- 0.75 ACH natural is way higher than current code max air leakage, and it's pretty cheap & easy to cut that by more than half with targeted air sealing. Defaults in tools are usually much bigger than reality. That's the biggest line-item number on heat loss at over 87oo BTU/hr. Reality could easily be half that, and half of 8700 BTU/hr is more than 10% of the calculated load. You'll get more comfort out of tightening up until than number is 2000 BTU/hr or less, and using heat recovery ventilation as-needed. What happens to the load number using the defaults for a tight house?

Window gains add a full ton to the cooling load (not surprising.) Even roof overhang or awning shading on the south side makes a big difference in the peak load, as does heat rejecting window film, particularly on the west side, since the unwanted solar gain occurs late in the day when the air temps are still high, and the roof/siding has been soaking up solar heat all day.

I didn't see any discounting of the heat load for 24/7 plug loads (refrigerators, cable boxes, DVRs, electric water heaters clocks, etc) or mamalian occupants. Figure 230-250 BTU/hr per sleeping human, and 3.412 BTU/hr for every watt of background plug load. A middle-of-the road refrigerator is 150BTU/hr, some are more. A top & bottom door Energy Star refrigerator is on the order of 100 BTU/hr. In most houses that adds up to well over 1000 BTU/hr, often more than 2000 BTU/hr.

A gasketed top sealing flue damper on the fireplace can cut the fireplace's infiltration losses by more than 75%.

The slab edge/floor losses of over 4000 BTU/hr might be worth fixing too, unless this house is on un-diggable soil, even though the IRC doesn't require it, but it's not a priority. Still that's over 10% of the calculated load. Even 1-1.5" of EPS dug down to a foot below grade on the stemwalls or slab edge can make a comfort difference at the wintertime low temps. Since you have the tool, see what adding R4-R6 at the slab edge does for the het load.

 

[Cr0ntab]

Looking into the app I see that for "avg construction" the ACH values are set to:

Summer - 0.4 ACH
Winter - 0.75 ACH

Changing to "best construction" the ACH values change to:

Summer - 0.2 ACH
Winter - 0.3 ACH

Updated "Tight" construction Calculations:

Heat Gain By Component
Heat Loss By Component
Manual J

---------------

There is no available shading for the windows on the south side of the house, they're too far below the roof overhang.

However, the east side of the home does get some shading on the windows with an overhang from the second floor and the roof overhang.

The west side of the house has an attached garage and some of the windows get a little shading from the roof overhang.

---------------

The calculations do include "people" for heat gain, that's listed as 4200 BTU/Hr

In the calculations I put people where the most time would be spent:
2x Office
2x Bedroom
1x Bedroom (2)
1x Bedroom (3)
2x Rec Room

This is probably high as well since it wasn't clear on where to put people in the calculations. I just assumed to put people during peak cooling load and peak heating load, which would work out to this:

Peak Heating
2x Bedroom
1x Bedroom (2)
1x Bedroom (3)

Peak Cooling
2x Office
2x Rec Room

The calculations also include 1200 BTU/Hr in the kitchen area for cooking (this probably also includes the refrigerator?)

We do have a newer top/bottom door energy star fridge, so that is probably closer to the 100 BTU/Hr you listed.

The laundry room is in the building envelope and that includes a newer washer and gas dryer

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I actually have a flue stopper for the fireplace in a box from amazon, just came today. I'll get that installed

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I walked the perimeter of the home and the east, south, and west sides all have concrete up to the slab. I would have to break out all that concrete to get to the edge of the slab, quite a bit of work and $$$. I may eventually get to the west facing slab because it's all cracked but that probably won't be for a while.

However, since I had the tool I punched in the calculations:

Updated "Tight" construction and R5 slab edge unsulation Calculations:

Heat Gain By Component
Heat Loss By Component
Manual J

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Lastly, here is a visual of the house layout. Not a floor plan, but just a visual aid.

North Face
East Face
South Face
West Face

East Face Window Overhang

The rooms in blue on the "West Face" picture share a wall with the garage.

 

[Dana]

It's definitely NOT going to be worth breaking out concrete to insulate the slab edges in your climate!

The south facing windows aren't doing too much for heating the whole house in winter, but are probably overheating that bedroom & rec room during the shoulder seasons. There's a fair amount of west facing glass that are raising the cooling loads for the rec room and family room on the second floor windows. The depth of the porch overhang is probably doing a lot to limit the gain from the family room's lower level windows. It might be worth installing some operable exterior "see through" shades (Coolaroo or similar) on those second floor windows.

The depths of the trellis roof on the east side means that it COULD be reasonably shaded in summer to limit AM gain, and left open in the winter for an AM solar warm-up, if you wanted to, with either an operable drop shade on the east side of the patio, or something over the top. With the cantilevered overhang the east windows are in full shade before noon at any time of year, but between dawn and 9-10AM when the sun is pretty low it can blast quite a bit of gain (welcome in winter, not so much in summer) into the east side rooms.

There's very little window gain or loss on the north side to consider.

 

[Cr0ntab]

Hey Dana,

So I followed your math in this thread:
https://terrylove.com/forums/index....olant-supply-line-to-attic.66546/#post-495152

and I came up with these numbers:

Use from gas bills
12/26/17-1/24/18 = 30 Therms
1/25/18-2/26/18 = 29 Therms

On this site I used weather station KCACORON41 (for zip code 92881)

With a base temperature of 70F (which is what we usually keep the heat around in the winter, 70-72F)

From 12/26/17 - 2/26/18 I added up 705.2 HDD

29 + 30 = 59 therms

59 therms * 100k = 5,900,000 BTU * 80% = 4,720,000 BTU

4,720,000 BTU / 705.2 HDD = 6693.1 BTU per HDD

6693.1 BTU per HDD / 24 hours = 278.9 BTU/degree-hour

Earlier you had stated that the 99% design heating temp was 34F for my area, so:

Using a 70F set temp

70F - 34F = 36F heating degrees

36F * 278.9 = 10,039.7 BTU/hr

Using a 72F set temp

72F - 34F = 36F heating degrees

36F * 278.9 = 10,597.5 BTU/hr

Do those numbers seem reasonable for a 2023sqft home with 2 occupants in southern california?

If so, our furnace is literally 6.5x (at low fire!) what we need. Seems kind of mind blowing (no pun intended)

Now that it's hot here, we've had a few really hot days and I'm working on gathering the data to do the same analysis with our A/C using the data from our ecobee thermostat. Still gotta figure out the math for this one though.

 

[Dana]

If you keep the place 70F, use a temperature about 5F cooler than that as the HDD base temp, assuming a not-super-tight 2x4 framed house with at least some insulation. With a reasonably tight 2x6/R20 house and U0.35 or lower windows (run of the mill low-E glass) use a base temp 10F colder than your indoor design temperature. The typical house's internal heat sources (refrigerators, mammalian occupants, cable box, water heater, etc) cover the rest.

The US standardized on base 65F back in the 1950s, when windows were all single pane, and many houses had no cavity insulation, and people heated to 7oF, give or take a couple degrees, and that model worked pretty well. The heating/cooling balance points were rarely more than a degree or two from 65F. Currently new code min-houses in colder climates have heating cooling balance points in the 58-62F range.

Also, the meter readings weren't at 12:01 AM on December 17, or 11:59 PM on January 26, so you shouldn't count both days. I downloaded a base 65F database from that weather station, added up the HDD from 12/17 through 1/25 which came to 554.5, then added up the HDD from 12/18 through 1/26 and came up with 560.4. (Fortunately there were no zero HDD days during that period, which can skew the result.) Averaging those two numbers gives you 557HDD.

So, 4,720,000 BTU/557HDD = 8474 BTU/HDD...

...divided by 24 hours yields a linear constant of 353 BTU per degree-hour

If you look on page 32 of this document (p38, in PDF pagination) you'll see that 34F really is the 99% outside design temp for Corona CA. (Your 1% outside design temp is 96F.) So the difference between the presumptive 65F heating/cooling balance point and the 99th percentile temperature bin is 65F -34F = 31 F degrees. That makes the implied heat load...

...31F x 353 BTU per degree-hour = 10,943 BTU/hr.

That's a bit higher than what you come up with using base 70F, but yes, that's the same range.

Now there were quite a few single-digit HDD65 days in that mix, and if you have significant solar gain on those days it could be skewing the result quite a bit since you might even have a cooling load on those days. Downloading a base 60F spreadsheet there were only TWO days during that stretch that hit double digits, and about 195HDD60.

4,720,000 BTU / 194HDD = 24,330 BTU/HDD,

/24= 1014 BTU per degree-hour

60F- 34F = 26F heating degrees

Implied load: 26F x 1014= 26,364 BTU/hr.

That's a big difference, eh?

So your real load is going to be between the ~11 KBTU/hr number using base 65F, and the 26 KBTU/hr number using base 60F. That's a pretty wide range, to be sure, but that's the error bars really are that high when the heat load is so shallow. But the load is almost certainly not MORE than 26,000 BTU/hr.

If you want to just split the difference and call it 18,500 BTU/hr or so it wouldn't be too far wrong, but I'd be very surprised if it were really as low as 11K. Most 2x4 framed 2000' slab-on-grade homes would have base 65F load constant in the neighborhood of ~600 BTU/degree-hour, give or take, when measured against colder weather than yours. ( 600 BTU/degree-hour x 31F heating degrees would be 18,600 BTU/hr. ) What's making it hard is just how not-really-cold your winter weather is and how few HDD there are to work with. This method delivers a much tighter range of results in Kalamazoo than Corona.

For the cooling analysis using the ecobee data it's easier to run a duty cycle analysis only on the hours of the day when it's a few degrees either side of 96F, don't try to use a linear approximation method the way we did the fuel use load calc. Copy the wunderground.com hourly weather history for the days you use, and don't use ecobee data for hours where the temps were more than 2F from the design temp of 96F. Do it for several days/afternoons worth when it was between 94-98F, not just a single day- the latent loads and internal heat sources will vary a bit, but by the time you have duty cycle data for 50 cumulative hours it should be pretty close. For more on using AC duty cycle for measuring the load, see this bit o' bloggery.

 

[Dana]

Quickly reviewing the Manual-J that came up with a ~29K heat load, the 2.3K fireplace & 3.5K infiltration loads may be unrealistically high, and the 4.5K floor load might be totally gonzo-high, depending on the actual conductivity of your soil. All together those add up about 10K, but reality might be half that, reducing the load to 5K.

There are also no deductions for plug loads or occupants. Most homes will have at least 2000 BTU/hr of 24/7 of refrigerator, cable box, water heater standby, and sweaty humans/slobbering dogs offsetting the load, and an aggressive Manual-J would take that all into account, as well as things such as window shades, etc- any reasonably justifiable factor that reduces the load number.

 

[Cr0ntab]

I'll start logging more as we have more days between 94-98 but so far two days in the last two months:

https://docs.google.com/spreadsheets/d/1eCQo8xur-xzAFWgg2IDlmkC5if86VJxdbO4k3zJg7SI/edit?usp=sharing

During the time the weather station temperature was 94-98F the compressor run time was pretty close to 78%

The weather station is down the hill from me, but still reasonably close. Right now my outdoor thermometer (shaded) is reporting 85F but the weather station is at 81F. I notice that pretty often, my outdoor thermometer tends to read a few degrees higher. But none of the data is logged so we can't use it

Question about the 1% outdoor design temp of 96F -- Does this take into account global warming and general temperature increases over time? I figure the ACCA folks account for this somehow in the number, but the document you linked was from 2011, 7 years ago.

 

[Cr0ntab]

Quickly reviewing the Manual-J that came up with a ~29K heat load, the 2.3K fireplace & 3.5K infiltration loads may be unrealistically high, and the 4.5K floor load might be totally gonzo-high, depending on the actual conductivity of your soil. All together those add up about 10K, but reality might be half that, reducing the load to 5K.

There are also no deductions for plug loads or occupants. Most homes will have at least 2000 BTU/hr of 24/7 of refrigerator, cable box, water heater standby, and sweaty humans/slobbering dogs offsetting the load, and an aggressive Manual-J would take that all into account, as well as things such as window shades, etc- any reasonably justifiable factor that reduces the load number.

I'll re-post an updated Manual-J with some of those changes.

I've since added a flue stopper for the fireplace which should drop the infiltration down quite a bit.

I've been stalking you online and reading a lot of posts you've responded to which led me down the path of calculating the heat/cooling loads via other methods. From everything I've seen you talk about the numbers in my existing manual J are off, but I wasn't sure how much. Using the hard data should help out though!

I started doing air sealing in the attic a few weeks ago but it's been roasting hot so I stopped. I want to get a bit more of it done before I call in someone to do a blower door test on the home and get some real ACH numbers.

All of this is in the vein of learning and preparation. The existing HVAC system is 12 years old now, still runs well and cools the home but I want to be ready when it's time to pull the trigger on a new system.

I plan to stay in the home for a long long time so any and all options are on the table:

ductless mini-split
ducted mini-split
air to air heat pumps
air to water heat pumps (chiltrix?)
conventional condenser + furnace (what I have now)
conventional condenser + hydronic coil (I recently bought an HTP Phoenix Light Duty, that thing is bitchin!)
heat pump + hydronic coil

All of this balanced by the fact that I recently installed a 10.89 kW DC solar system capable of covering my entire usage and then some (the extra to be reserved for an electric car or two down the line) with my existing 5T A/C power consumption, so this means comfort outweighs efficiency (to an extent) when I eventually do the swap.

I'm really really picky when it comes to the equipment on my home, I'm a tech geek and love being on the edge of things. (I don't mind tinkering with stuff to get it working perfectly -- just ask my solar contractor...that was a love hate haha)

Not to mention I love doing all the research

 

[Dana]

I'll start logging more as we have more days between 94-98 but so far two days in the last two months:

https://docs.google.com/spreadsheets/d/1eCQo8xur-xzAFWgg2IDlmkC5if86VJxdbO4k3zJg7SI/edit?usp=sharing

During the time the weather station temperature was 94-98F the compressor run time was pretty close to 78%

The weather station is down the hill from me, but still reasonably close. Right now my outdoor thermometer (shaded) is reporting 85F but the weather station is at 81F. I notice that pretty often, my outdoor thermometer tends to read a few degrees higher. But none of the data is logged so we can't use it

Question about the 1% outdoor design temp of 96F -- Does this take into account global warming and general temperature increases over time? I figure the ACCA folks account for this somehow in the number, but the document you linked was from 2011, 7 years ago.

The binned hourly data from which the design temperatures are determined are the 25 year averages, and I believe with both ASHRAE and ACCA the design numbers are updated every decade, not more frequently, so the last up date was 2010(?). A 1% outside design temperature of 96F means that in the 25 years prior to 2010 only 1% of all hours in that time frame exceeded 96F. In an average year that would be 87 hours. But not all years are average years- some much hotter, others much cooler. Over the course of the last 50-100 years design temps may have moved up a degree or three in some locations, down a couple in others, all in response to climate change (including global warming and the changes in both atmospheric & ocean current patters.)

 

[Cr0ntab]

We had some pretty hot days in July so I updated the spreadsheet with more numbers:

https://docs.google.com/spreadsheets/d/1eCQo8xur-xzAFWgg2IDlmkC5if86VJxdbO4k3zJg7SI/edit

Here is the weather station data:

https://www.wunderground.com/person...wx_pwsdash#history/s20180706/e20180706/mdaily

On the hottest of hot days things are still oversized, but not by very much:

(5 Tons) 60,000BTU * 88.83% = 53,298BTU

53,298BTU / 12,000BTU = 4.4 Tons

This exercise has definitely been eye opening for me.

------------------------------------------------------------------------------------------------

I'm currently exploring options for insulating the attic a bit more to cut down some of the heat. I also have a few more areas to air seal on the second floor ceiling.

I'm also evaluating a high performance window in the master bedroom, it's a 94" x 58" window so quite a bit of glass but so far so good.

The installers had already taken off the NFRC label by the time they got here so who knows where it went.

However the window configuration program said that the unit had a U-Factor of .28 and a SHGC of .15, but I'm not sure if that's whole unit, center of glass, or what.

The window was spec'd with Lowe 340 glass and a SuperSpacer non metal spacer.

The glass definitely has a blue tint but we (the wife) have gotten used to it and it's not too bad, heat is definitely cut quite a bit.

We don't have funds to do all the windows at once so I'm going to focus on my manual J results and do a few windows that have the highest heat gains next.

This is our first summer in this house, and it's definitely gotten much hotter than I gave things credit for.

------------------------------------------------------------------------------------------------

From some more research I've also adjusted my options list:

ductless mini-split
ducted mini-split
air to water heat pumps (chiltrix?)
conventional condenser + furnace (what I have now)
conventional condenser + hydronic coil (I recently bought an HTP Phoenix Light Duty, that thing is bitchin!)
heat pump + hydronic coil

There isn't a lot of local support for the Chiltrix gear and the few folks that do work with it want to charge absurd amounts of money to do/plan anything.

So while the efficiency of that system is quite compelling, the costs outweigh it especially with other heat pump options.

Also, researching the available heat pumps, nearly all of them can cope with the rather mild winters we have here so no need to have "backup heat" from a hydronic coil fed by the HTP water heater.

I'm on the fence about a DIY cheap mini-split install but I need to work on unit placement. I know Dana has spoken about issues with "micro zoning" with a head in each room approach.

I figure if I put in a DIY mini-split setup I still have the regular ducted HVAC system as backup in case things go terribly wrong, but I can net some energy savings earlier.

Sorry for the long rant, been a while since the last update so I figured I would just brain dump!

 

[Dana]

Window manufacturers are required to use the U-factor & SHGC for the entire unit, insulated glass manufacturers can only report the center of glass numbers. As a general rule the U-factor of the whole window is higher than the center of glass numbers (sometimes by quite a bit), and the SHGC numbers slightly lower than than center of glass (sunlight doesn't pass through the frame, only the glass.)

Warranties notwithstanding, shorter longevity of cheap mini-splits may erase some of the energy cost savings by more frequent replacement/repair.

The average duty cycle over the hottest full days isn't quite as relevant as the average duty cycle over 3-4 hour period immediately before & after the outdoor temp crosses the 1% outside design temperature. The high duty cycle periods in the spreadsheet were over 11-13 hour periods, but the average & peak temperature over those periods aren't reported in the spreadsheet.

Ductless solutions don't have duct & distribution losses adding to the load, so if the loads were calculated on the duty cycle of a ducted system going 15-20% smaller in AHRI capacity than the calculated load is only rarely going to be a problem.

 

[Cr0ntab]

I've been at the house for almost a year now.

I found a new cool app called BeeStat that outputs fancy graphs from the data gathered from my EcoBee, see attached!

https://drive.google.com/open?id=1hcFgu8a4frTKCyr9jW8GTlVSyi-GVknu

As a running tally of improvements to the house.....

Front Door
I've added a bit of adhesive weather stripping around the front door.

It helped for sure, but it's still drafty. I think it's on the list for replacement as it's a bear to open (the door is swollen or warped I think) and the wife hates that. So we'll likely take the time to replace it with a nicer fiberglass insulated door.

Attic
It's cooled down quite a bit since summer so I've gotten back up into the attic to look around.

The good news is that a lot of the original holes in the building have already been foamed! So a lot of the work has been done which is great.

The bad news is that the usual suspects need to be fixed. I saw a lot of dark insulation around all of the can lights, around all of the bathroom vent fans and around many of the ceiling fan fixtures.

High Performance Attic
Since it's cooled down I'm now going to embark on the work to insulate the rafters and create a "High Performance Attic - Option B" as per title 24. I am in the right climate zone to do this, I have a concrete tile roof which has an air gap on the exterior sheathing, so all the boxes are checked.

https://title24energyreports.com/articles/high-performance-attics.php

The roof is held up by trusses that are made of 2x4's spaced 24" O.C.

I'm going to be installing RockWool in the rafter bays between the studs. I like working with this insulation over fiberglass. It's much more rigid, and I likely won't have to use hangers to keep it in place.

https://www.lowes.com/pd/ROCKWOOL-R...-with-Sound-Barrier-23-in-W-x-47-in-L/4382951

From my modeling in Wrightsoft it doesn't appear that it will make a material difference in building loads. It might have a more material impact on the longevity of the existing HVAC equipment though, so that's a plus.

I guess it's new code for a reason and it's not that hard for labor so we'll try it.

Recessed Can Lights
I'm going to be replacing all my can lights with slim IC LED fixtures. (Wife doesn't want flush mount lights and the holes are already there) Something like this:

https://www.homedepot.com/p/Halo-SM...557078?storeSelection=6665,601,1084,6619,6643

These should be much easier to seal. I'm also going to foam around all of the fan fixtures to clean those areas up.

Bathroom Fans
When I went around and sealed all of the HVAC registers I didn't think about the bathroom fans and sealing those.

While in the attic I discovered that these were REALLY bad spots for infiltration. Even more so than the can lights. There were huge gaps between the fans and the drywall.

I'm going to foam the edges and tape seal just like I did on the HVAC registers, that should fix those up.

With the can lights and bathroom fans taken care of the only huge remaining hole in the attic/ceiling partition is the attic door. I need to figure out a good solution for that. It's got some incredibly convenient stairs mounted in the hatch.

The original design was just a piece of drywall that sat on a lip to fill the gap. That's easy enough to fix with something like this:

http://www.batticdoor.com/atticaccessdoor.htm

but I really really really like the stairs.....I have some thinking to do.

HVAC Duct Leakage

While I was in the attic I went ahead and kicked on the heat and walked around with a FLIR thermal camera.

I was surprised to see that 90%+ of the ducts were sealed quite well. I didn't see any leaks on camera and I confirmed with a smokepen and my hands.

However, I did find a lot of leaks around the plenum takeoffs. I'm going to seal all of that up with mastic to get rid of those leaks.

It was great to find this though, it definitely confirm's Dana's thoughts and experience.

Last winter when we moved in I ran the heat quite a bit. I'm sure these plenum leaks existed then and REALLY drove up infiltration. I had complained a lot about low humidity in the home during the winter so I'm hoping all my sealing work will help combat that this time around.

Modeling

I was using HVAC Calc to do my Manual J and load calculations but I just didn't trust it. It didn't offer a lot of detailed data input and was mostly high level. So, I broke down and got a year subscription to Wrightsoft. This tool is the beez neez! It will let you hang yourself with options!

I went ahead and re-modeled my home with Wrightsoft and took care to enter as much detail as I could, results of that are here:

https://drive.google.com/open?id=1m6H7BrkEWSCv6SpLtC1vg5cAsskWI7A6

The one thing that matches with HVAC Calc are the fenestration/glazing loads. The east/west facing windows add a lot of heat to the home. While going around and re-measuring everything to put into Wrightsoft I also noted that the old windows were quite drafty. It rained the last few days and I could feel gusts of wind coming through the windows as I was measuring, not ideal!

As such, we'll probably start replacing those with upgraded units like we did in the master bedroom.

It's also not entirely accurate as I haven't gotten a blower door test done. I want to finish up the air sealing so I can get a blower door test done. Then I can input that data into Wrightsoft and get some more accuracy.

Equipment

ductless mini-split
ducted mini-splits
air to water heat pump with fan coils
2x zoned heat pumps + hydronic coils

I've been continuing my education on mechanicals and I've re-warmed up to the idea of an air to water heat pump.

I really want to microzone my home. The cool factor is high for me and I love the flexibility it gives everyone.

Everyone tends to sleep with doors closed when we have visitors and I expect that same behavior to hold true for the future.

When the inlaws came we had the AC on and they ended up closing the registers in their rooms. Which caused them to start whistling from the increased velocity! They were cold, we were not. This added some more ammo for the zoning proposition.

Pouring over tons of submittals for ductless mini splits, the room loads are just too low from all the manual J's I've run.

The only way this could potentially work is to stack a bunch of single zone units outside, but the wife quickly veto'd that idea.

I can come close to micro-zoning with ducted mini-splits and just making a few zones for the house, but it's ducted and still less than ideal.

In my reading I've learned that with the use of buffer tanks, hydronic heating and cooling can quite easily be microzoned, without short cycling compressors.

There is also a huge DIY factor to hydronics for me. I can run plumbing all day long. Unlike mini splits, I don't need a refrigeration cert or any special equipment to charge it up.

The jury is still out on what I'll end up with. I want to get all my house loads dialed in before I search for equipment.

After reading a lot of John Siegenthaler's papers on hydronics I'm really really liking the idea.

That was a lot of text, but it's just documenting my journey.

 

[Dana]

The 3" fire protection/sound abatment batts are only R11.7. The 3.5" rock wool batts (fits 2x4 framing depth) are denser, and R15. Any of them will come down in an earthquake if not constrained. Holding them up with perforated aluminized fabric type radiant barrier stapled to the underside of the top chords of the truss will also take some edge off the peak cooling load without risk of trapping moisture the way other types of RB can.

A reversible chiller, buffer tank, and individual room coil solution is quite flexible & effective, but not cheap.

Hopefully the window leakage can somehow be tightened up rather than replaced. Sometimes a tight l0w-E exterior storm window can work when no amount of weather stripping can, but in high sun area that risks heating up the glass of a low-E U0.28 insulated glass unit enough to blow the seals. Tread cautiously.

 

[Cr0ntab]

High Performance Attic Update

I previously said "I guess it's new code for a reason and it's not that hard for labor so we'll try it."

This work is definitely harder than I gave it credit for!

It's going slow but it's going, forgot to take pictures of tonight's efforts but it's about double what I have in the photos.

EDIT - Link to photo album

https://photos.app.goo.gl/D8oUos6pUA85MRHbA

I tend to get through two bundles of insulation each "session" which is 16 batts each time.

I ended up buying this insulation:

https://www.insulation4us.com/roxul-comfortbatt-r15-3-1-2-in-x-23-in-x-47-in-12-bags.html

Fits well, but not as snug as I would like hence the strapping to hold things in place.

Once I get all the insulation up I'm going to staple up some perforated radiant barrier, but at my pace it'll probably be a month or two before I'm ready for that.

Slow and steady....

 

[Dana]

The pictures didn't seem to show up, but keep plugging away at it. It will be worth it in the end.

 

[Cr0ntab]

Not sure why the photos didn't show up, I updated the post with a link to the album instead.

 

[Dana]

Sorry that I didn't flag this earlier, but IRC code requires either a 1" air gap between the insulation and roof deck, or (in your climate) R5 on the exterior of the roof deck with the batts snugged up to the under side of the roof deck. It looks like you have 3.5" deep top chords to the trusses and 3.5" batts- no air gap. Re-roofing soon? (Didn't think so.)

Rock wool batts are air retardent enough that they don't really need a top side air barrier. The gap issue can be fixed by installing 2x2s (1.5" deep) on the underside of the truss chords to staple the perforated RB onto, leaving 1.5" of air between the roof deck and batt.