Old Construction R-values

delta T

Any one have any experience with heat loss calcs on old (late 1800s) houses. My Father just bought a house that was built in 1881 and wants me to do a heat loss for it. Construction is double layer brick with lathe and plaster inside and plaster outside. I do not know if there is an air gap between brick layers or not, or if that will make a significant difference or not. I have Siggy's HDS and there are obviously no pre-set wall assemblies close to this so I'm gonna do have to come up with the value myself.

Any pointers anyone would care to share? Just a little nervous as the values I'm dealing with are so low that making a mistake on the R-value somewhere could have a significant impact on the final result.

I am planning on using 1 ACH as the house is pretty leaky. Should I be higher than that? single pane windows for some but most have been replaced with double pane vinyl, so that's good. The doors have poor seals though, and I am sure there is a significant amount of leakage through the walls themselves.

Thanks in advance for any pointers or tips that anyone would care to share!

Harvey Ramer

4" face brick has an r value of .44 and 4" common brick has an r value of .80 . An air gap from a minimum of 1/2" to a max of 4" has an r value of 1.

Gordy

You have mass with all that brick. That is favorable.

delta T

Yep I was thinking of that Gordy, hopefully it helps. Appreciate the R-values Harvey, big help.

Any thoughts on ACH? Think I am going to far with 1 or should go even to 1.3? I think that is my biggest sticking point right now. I don't have a good feel for this type of construction and I don't know if any of the old rules of thumb will be on point or not.

looks like the original heating system was a coal gravity furnace, there is an old coal chute and port for the old auger, (all gone now) but the original ducting (asbestos and all) is still there. I'll post a pic in a bit of the old water heater. Looks like it was run off the coal furnace with a coil? Not really sure. There is no evidence that there has ever been a hot water system.

delta T

Here are some pics of the water heater

delta T

delta T

never seen one like this before, thought it was pretty cool!

SWEI

My experience is that mass (when properly utilized) tends to offset infiltration, often considerably so. A multi-day major storm could negate that, however. Those are quite rare in this part of the country.

delta T

This is in Trinidad, CO and is going to get a FAGF unfortunately so mass will be harder to utilize to full effect. I just finished measuring everything up, I think I am going to go with 1 ACH for the places that have doors and single pane windows, and plan on .7 for rooms with just the single panes, and .5 everywhere else. I think that will give me a decent number. Plan is to put in a 2 stage 90+ furnace, with the sizing for the first stage being able to cover about 70% of design day load (80 delta t) and the second stage will then be able to take anything that is thrown at, even if my numbers are off.

Appreciate the comments, I'll let you know what it ends up at.

Bob Bona_4

I'd use the default of 1.44 ach per my man J. "Old homes/farmhouses; poor tightness". FWIW.

Sal Santamaura

delta T said:

Here are some pics of the water heater

Interesting. On a recent "American Pickers" episode, they bought a stand like the one under that water heater. Mike Wolfe didn't know what it was, but the guy who sold it did, and he shared that information. Great to see it as originally used.

Harvey Ramer

ACH is riddled with uncertainty and has no really good numbers. Even if you do a blower door test.

In a large open area, the ACH number should be dropped while in the same building, if you have a smaller area with 3 exposed walls, the ACH number should be raised. The 2 areas should also be zoned separately so none of the areas overheat or under heat when the wind is not blowing.

If you apply a percentage factor to the ACH number based on square footage of different areas and end up with the sum of both areas equalling the total ACH number, you should be close.

Gordy

Location, location, and orientation. Is it out in the country on a hill in the open? Or in town with houses on both sides, and behind?

Zman

In a similar construction in Denver. 1,800 square foot structure heated with a furnace, output 60,000. It runs about 60 percent of the time on design days.
I suspect the calculator will give a number 30 something per foot. In reality it is in the 20's. The high mass is a big factor.
It takes about 10 hours flat out to raise the temp 10 degrees. I would not recommend a setback.

SWEI

Hydro-air with ODR could help tame that mass.

JUGHNE

There may be an air gap between the inside wood lath and brick. Maybe only 3/4" or less as often 1 x 4's "studs" are nailed onto the inside brick. A 1/8" drill bit penetrating the plaster & lath would let you know of that space. I would drill several places until the bit was worn out and then throw it away.

The outside air space might be checked with a 1/4" bit in a hammer drill, go thru the "tee" intersection mortar joints at inconspicuous places and "feel" for any spaces. Caulk your exploratory openings shut when finished.

Or if possible you might pull the dryer vent out, that might give you a hand inside the wall. FWIW

delta T

Thank you guys for all the comments!

@Harvey Ramer I can't zone it, BUT....whoever did the initial installation installed dampers on every one of the supply ducts so at least we have some flexibility to balance the system out. We did a static pressure test with the old blower and it looks pretty on point which is nice.

"If you apply a percentage factor to the ACH number based on square footage of different areas and end up with the sum of both areas equalling the total ACH number, you should be close."

I will do that and revise my numbers tonight and see what happens, thanks!

@Gordy It is in town and it is small compared to the houses on either side, so it will get some shading in the morning and afternoon. long kind of skinny lot with the axis of the sun's movement (E to W) is perpendicular to the long axis of the lot. There will not be a lot of solar gain on the brick. The original part of the house is double layer brick, but as it turns out more than half of the house is stickframe with siding, only about r10 vermiculite in the exterior walls, but certainly better than the brick!

@Zman Thats good to know thanks, I will keep it in mind.

@SWEI I agree, would be nice to put in hydro air, but not in the cards right now. Maybe later! maybe down the line I can convince him to let me put in a hydronic system. Thinking of some nice old cast iron rads with modcon and TRVs with ODR. maybe.....

@JUGHNE I did find two places in the wall that are exposed enough to see the construction. There is no air gap, it is stucco on the outside and two layers of brick with no gap (it is filled up with motor as far as I can see) and every now and then there is a piece of wood sandwiched in the brick to nail the lathe onto, not really any air gap there I suspect.

As of right now I have a number of a touch less than 60,000, I'll play with the numbers a bit and see what size furnaces I have available. The only local parts supplier is an hour away, so I think my dad is going to want to go with something they stock parts for. This will not be continually occupied for a few years yet.