Sustainable heat and hot water: approach review

Joe Brix

The piping may not lead to seperate systems for each unit.
It get's sticky with condo's. Usually older builings go co-op because of shared services. I think a small seperate mod/con gas wall hung boiler for each unit is the best way to go. If you have to repipe the rads, just go radiant flooring instead.

waterfront

Sustainable heat and hot water: approach review

I am renovating a 3 unit row house into 3 condominiums.

The goal of this project is to make it a demonstration of how a how house can be done as sustainably as possible. To point a fine point on the sustainable “goal” I am shooting for (I’m hoping this word does not derail the conversation) I am focusing on minimizing energy usage of the building. For the below query, assume that the walls are min R25 and roof is min R50 and the envelope is very tight. Given that, I’m turning to questions I have on heating and domestic hot water.

Q1
The current systems are cast iron radiators. Given the efficiency of the envelope, I have been advised that the heating requirements will be minimal…and from a cost standpoint I think keeping the existing radiators or upgrading to the steel plate variety so that individual rooms can be controlled to minimize heating costs. Any thoughts on this approach?

Q2
I have also been advised that a single new condensing boiler with an indirect hot water heater for all three units together would be the most efficient use of energy as it will supply both heat and domestic hotwater for all three units. I have several concerns about this approach.

First, these are condos, and separate metering would be challenging, if not downright impossible …has anyone had any experience with implementing such a system?

Second is it possible to do on-demand hot water to a indirect tank to supply both the hydronic heat and domestic hot water? It seems to me I might get the same energy efficency with that system at a reasonable cost and the ability to separately meter as well.

Third, can I do three on-demand systems without the tanks, given these are 1,000sf 2br/2ba units to supply both the hydronic system and the dhw? This is a market (the metro DC area) where it is highly likely these units will have 2 adults, no children occupying them so the flow demands seem achievable.

Your thoughts will be greatly appreciated.

Waterfront

Steamhead (in transit)

I'm assuming

that the existing heat system is hot-water rather than steam?

If so, the existing cast-iron radiators are fine. They'll just run at a lower temperature. For individual room control, a thermostatic valve on each radiator is the way to go. The boiler in this case would be controlled by an outdoor-reset control that would vary the water temperature according to the weather.

The advantage of using one boiler to provide heat and hot water for the building is that all your combustion is located in one place that is easily accessible for servicing, and can be kept locked to prevent tampering. This location can also be made fire-resistant. You could also have three separate boilers in that one space.

Not sure if on-demand water heaters are approved for space-heating use in D.C. Someone would have to check with the Code authority which I believe is WSSC.

If you end up not using separate metering, the heat and hot water could be included in the condo fee.

Have you contacted Dan Foley, of Foley Mechanical? He has much experience with this type of system. Go to the Find a Professional page of this site to find his info.

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waterfront

Steamhead-

Yes, it's hot water, not steam.

Yes, it would be easy for a single boiler system...but i'm trying to directly tie a persons usage directly to where it will impact them the most: thier pocketbook. Common systems (in my experience) lead to waste when it comes to heat and hot water. I'm very concerned that any efficiencies gained by a common system would be obliterated by a common usage scheme...so having separate metering is pretty important to the sustainability goals of the project. Also, it's a demonstration project...and that means both for the end users, but also for developers who argue that it is too expensive to do a green renovation for a rowhouse. However, when i get the options costed I may have to change my tune and think of creative ways to encourage thrifty use.

I'll have to check DC code on tankless use for space heating. Good point.

Thanks to the reference to Dan Foley. I need a designer/installer from his example project he looks like a solid potential fit.

Waterfront

Perry_3

Be sure to include

appropriate sized air to air HX to ensure sufficient fresh air in the house.

This is proabably the biggest mistake of "tight envelope" houses.

You NEED to have a certain amount of air flow.

A good Air to Air heat exchage system will recover most of the heat. It will also include air filtration.

Alternately you will have sick house and mold problems.

Perry

Unknown

If you have very low heat loads, You might be able to use tank water heaters to heat with.. I wouldn't go with a tankless, it would be less efficiency on a low load system than a decent tank heater (for heating loads). The additional efficiency of 3 mod cons on 3 sub-20kBTU/hr loads in your climate is unlikely to be cost effective.

I would instead go for tank heaters, most likely, and focus more on the envelope to absolutely minimize the loads (better glass, for instance). You would have to separate the water heaters from the radiators though.

First thing first would be to run load calcs and see if those radiators would do the job with lower water temps though.

Mike T., Swampeast MO

If your prime goal is to reduce energy consumption as much as possible, here are my recommendations:

1) Use a single condensing/modulating boiler.

2) Install thermostatic radiator valves (TRVs) on ALL radiators.

3) Use an indirect water heater of generous storage capacity.

4) Presuming you have suitable roof space, install solar panels for DHW heating and/or DHW pre-heating.

This will keep the installation costs reasonable compared to using individual boilers for each condo--which would almost certainly require significant or complete re-piping. A single (or staged) mod-con will require very little in the way of piping changes.

The TRVs will allow quite a range of individual control--both among and within the units.

The only real drawback is a lack of individual metering for the condos. Presuming you create an extremely efficient shell (sounds like you're going to), space heating costs will be very low and surely an equitable arrangement can be made for splitting the fuel cost. Proper setting of the boiler's heating curve will allow sufficient heat everywhere with a reduced chance of anyone being able to keep their unit excessively warm.

If a Vitodens by Viessmann is used (highly recommended) I would suggest running a cable to allow remote control of the boiler to each unit. Only one can be used at a time, but it would allow the owners to elect one of their own to act as the "energy watchdog" and balance performance with efficiency. Once a good setting is established that keeps everyone happy both with performance and fuel costs, there would be little or no need for change unless the tenants themselves change.

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

If you utterly need independently metered heat sources, so-called "combi-boilers" could be used. These are condensing/modulating boilers with a built-in heat exchanger to provide "tankless" domestic hot water. Considering the size of the units, they [should] be able to provide sufficient DHW.

Unfortunately though the boilers will be greatly oversized for space heating.

In this case I probably wouldn't use TRVs, but you'll almost certainly need a complete re-piping. Why no TRVs? With such a small heating load a traditional on-off thermostat [should] at least allow the boiler to fire at or near minimum output during the heating phase. If TRVs and constant circulation were used you'd wind up with a constant TINY load requring the boiler to cycle very frequently.

Provided you use the existing piping and radiators my guess is that you could install a single boiler of the finest quality, TRVs and solar DHW to boot for near (lesser quality materials/control in the three systems) or even significantly less (same quality materials/control) than the cost of three individual systems requiring a complete system re-pipe.

Chris_82

well said,...

When people "feel" they have some sort of control over their utilities, generally they have a more sustanable project and although initial costs are slightly higher for dupilicate meters and such the enviormental costs and fuel saving far outweigh those costs. In other words having to pay what you use saves energy, but more happens when people feel they have a sense of control. How stuff gets percived is frequently more important in the long run, this is why most utilities are welcoming individual services and meters despite the widely held perception they do not. However there are enough backwoods utility suppliers out there to make their ignorant voices herd when it comes to multiple meters as an example, they only see increased paperwork and that kind of hassel for their shortsighted interests. What you need to to keep in mind is that this type of utility supplier is like the dinosaurs they just don't know it. Fortunatly there are a number of national programs designed to assist these types with their thinking, unfortunatly sometimes you need a lawyer to get individual metering but in the long run there is little dispute about the energy savings and never mind the lessining of problems for the funders to any project...sometimes pointing out to your banker about some of these issues and how sustanable projects have these individual versus common services ironed out before the project starts and how everyone gains by this type of thinking versus the shortsighted local utility.

Mike T., Swampeast MO

In my area utility companies greatly prefer individual metering--using THEIR meters! After all, more meters means more customers and more "basic" monthly charges! What they don't like (and I believe expressely do not allow) is sub-metering. In other words you can't install your own meters after their meter to divide charges.

Unknown

What if you just put in some data loggers and did basic division

Chris_82

this may be changing in some areas as well,...

in Revere Ma there was strong local resistance to pay the sewer charge as far as dw was concerned, so they started to let the public add additional meters, as long as john and jane public payed for them and they were inspected and tagged with the anti theft couplings and seals, then many started to "suggest" the local gas supplier do something as well, as far as I still remember For a blighted town/city they were pretty progressive as far as this issue was concerned as compared with Brockton and Lowell Ma that you usually end up getting a lawyer to assist with the same issue! As time goes on I'd immagine the fed will start appling real pressure for those that request multiple meters as there is little dispute that in each and every case they save fuel and energy.

waterfront

All-

Thanks so much for your input...comments follow:

Chris- thanks for your support. Utilities are a nightmare to deal with on any size project (i currently consult on a very large project in downtown DC and even with the developer being very assertive, the powers that be have managed to delay thier job 3+ months.) a small project like mine has very little chance of registering on the radar, no matter what my sustainability goals. so as much as i can avoid causing any waves at the utilities thats going to be my approach.

Mike T - really? submetering is illegal? i have thought of submetering the water use and doing straight division to apportion...turns out that companies dont really make meters that will handle hot water. i only called Neptune, so perhaps i am wrong. A funny aside, this row house has a metered subpanel for the electrical for one of the units. It's a real headscratcher for most contractors.

Perry - ERV's are part of the planning...still working it out, but i know i need them.

Joe Brix - i will have to repipe the rads, all of the copper in this place is pitted severely and the cast iron pipes are just in the wrong place in the basement. i nixed the radiant flooring idea...just not cost effective, especially given that the piping for nearly all the radiators are very exposed and there will be a common chase to get from the basement placement of the boiler to the 2nd floor. I started enamored with the idea of radiant floors until i had the epiphany that the heating loads will be so low that i could easily reuse the radiators.

NRT.Rob and Mike T -
Given the above statement about needing to do a complete repiping can either of you expound on the 3 mod/con approach? I havn't looked into them too much, but they might be a better fit, given your comments.

Q1: Can you describe the animal and give me some sense of the unit cost for a small one?
Q2: Can you tell me any draw backs for them?
Q3: How small can they be? Like i said, there is a common chase where i could actually site these if they were petite. That would place each on a floor and minimize piping runs to under a 20' max distance to the farthest rad. It seems like something to consider.
Q4: More generally, what temp will a cast radiator run at? I have read a baseboard heating system would run to hot a temp to have the condensing function of the condensing boiler...i am assuming that there will be no difficulty with the cast rads.
Q5: I am not a plumbing professional and will be getting in touch with some ASAP, any recommendations on how i could run basic load calcs, given i don't have any software?? I just want to know that i'm not wasting time with this approach.

With respect to solar DHW, given the 95% AFUE efficiencies that i can achieve with a condensing boiler and indirect tank, do you think it's still worth it to pre-heat with solar? Won't it come in too hot for the condensing boiler to operate efficiently? Also, seems like the payback time would be 10+ years (as opposed to the normal 5ish years that is commonly bandied about) given the loads. Am i wrong about that? Also, if I am intending to use GFX technologies to preheat using the shower water (which is much lower cost than Solar) won't that further stretch out the payout time for the first costs? Am i over thinking this? I apologize for the cluster of questions...i am working through my due diligence on this stuff and you all are really helping...

Thanks again, all.

Waterfront

Mike T., Swampeast MO

Can't reply to everything right now, but sub-metering is a very touchy subject. Ask the utility provider anonymously if such is allowed. If they say "no" and you do it anyway there could be a GIGANTIC legal headache if any of the unit owners ever complain about "their share" to the utility!

Mike T., Swampeast MO

re: Repiping

If you have standing iron rads the original piping was almost certainly iron or steel. VERY long lasting in a closed system. My most sincere advice regarding old iron/steel piping "in the way" is to first deal with and design around the mains and relocate branches in kind if utterly necessary.

You mention pitted copper. If this is piping near the boiler it will be replaced (where necessary) with the boiler.

Or perhaps the copper is in modifications leading to radiators?

Chris_82

you should also be aware that to be considered a condo is to have seperate utilities, this varys widely also. But more than one sale has been held up by the banks insistance that seperate meters (due to potential water leins) be satisfied before a sale is allowed. In most of MA and NY a condo is considered seperate and has to have sepeerate utilities or in fact is not considered a condo but this is still very looosly enforced. Pressure comes from many sources not just difficult utilities.

waterfront

All-

there is both original iron piping, which is fine. There were add on rads in one location in the house and they have copper. I am considering if i can keep the original mains, but as it's a basement i have ceiling height issues and i need to move at least some of the piping...moreover the new boiler(s) would be in a new location and automatically that means reconfiguring some of the iron.

I don't know if DC requires separate metering for all utilities, in particular water. Electric, gas, yes. But, for example, this is currently a legal two unit and it has common water. That is an exceedingly common situation...i will have to ask counsel. Honestly, that could break the deal right there...and then i'd be doing apartments!

Dave_4

just stumbled into this discussion, but since it's not too old...
i have been working with the submetering issue in NY. instead of dealing with legal issues, i decided to include the utilities with the rent based on the high-side-of-estimated utility use, with the rent charge changing based on the season. there's a caveat to the tenant that they could receive a refund for a month, or their rent could be raised, based on their consumption pattern.
this way you are not acting as a utility, avoiding that legal question. you are just tailoring your rent based on your costs (which, if spelled out for the tenant, should be fine).

tom

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scott markle_2

utilities included

Tom are you saying that you will use degree days to adjust rent based on weather conditions? fuel price volatility would also be an issue. I have been wondering about these issues. I have a land lord client who has some very inefficient equipment at his rental but there is very little incentive for him to upgrade as tenants pay utilities. This guy really does care but it's hard to shell out for ideals alone. Please elaborate on your contract with tenants.

Perry_3

Submetering

Actaully; I'm quite sure that properely structured submetering would be allowed everywhere. The problem is the cost of proper structuring - both mechanically and legally.

One thing that I note is that you would need a source of calibrated meters - and I can easily see where you would need to track not just water usage but temperature in and out as well; and you would need separate meeters for the common areas of the building so that no appartment (or condo) would be paying for heating the common areas.

This is nothing more than how district heating (and cooling) systems work. Each building is submetered for their usage (and sometimes individual major customers within a building).

The question becomes how do you set it up for an appartment building - and is it worth the cost.

Seems to me to be something that is much easier to do with original construction.

Perry

Chris_82

In most states two theories of Law apply tenant at will or tennant at notice. In other words tennant at will which is 30 days and in most all states requires a (month plus a day ) notice to quit. And lease holders with signed contracts. In most all states leases require notice and since your scheem is indetermined you have just given any lease holder the right to quit or terminate without notice or cause. The same rights do not apply to the lessor. As far as monthly rates that change generally if the tennant agrees to this by paying after the fact your good! But if the tenant disagrees by refusing to pay, which they have a right to do, you have absolutly no remidies whatsoever! Because in a nutshell you have stipulated a rent increase with out notice. The law is signifigantly different for tennents that pay weekly or daily as in rooming houses which is why they are called rooming houses. Generally the law takes a dim view of changing rents, which defeats the idea of monthly rent, they veiw it as "your trying to beat the system" regardless of your good intentions. This is why, once again, in the long run seperate utilities with seperate meters. And Perry with all due respect there are already substantial laws on the books regarding individuals from NOT distributing or charging for utilities that are already highly regulated by law! This has been going on since edison put lights in Flushing.