Hello,
I need guidance on parameters for designing my energy system on a vacant 6 unit apartment building. 

The 1907 house is framed in rough cut 2x4s, has vinyl siding, and a few layers of shingle, thin styrofoam..   It presently has no insulation.  My plan is to insulate the house from inside, install a solar hot water system, and the best heating system I can afford.

Radiant in the whole building seems out of reach.  Beyond the expense, tt would involve tearing out nice floors or going over them, breaking fine plaster work etc...  It may be more feasible on the 1st floor in a between floor joist installation. 

Can anyone offer a suggestion regarding:

Is blow in cellulose a good solution for 2x4 plaster walls?  If not what would be better for intact walls?

If radiant is out (??), what is the next best solution for hydronic heating?  Radiators, what kind, low temp high temp?  Baseboard?  Radiant wall?

Should I try to integrate the solar input into the heating system or just keep it for the DHW?

In my case (solar input, 6 units, a combination of radiant and other hydronics) what would be a suggestion for the array of boiler/tankless/hot water tanks (the less machines the better), keeping in mind that I will need to meter the energy use (otherwise people open windows in january...)?

Any suggestions would be greatly appreciated. 

Bisseti: That really can't be answered until you know the heat loss & infiltration factors in the building, and maybe until have finished insulating and air sealing the house. You can have blower door tests done on the house now to get a starting point and have asome analysis done based on insulating and air sealing to a certain point. Keep in mind that up to half of the heat loss in the house may be related to air infiltration, so you should devote a lot of effort into sealing the envelope. Look for holes into the building from the basement, seal the rim joist/sill area, pull up the attic floor & seal all the penatrations into the attic, weatherstrip all the exterior doors and windows. Good luck with the project.

Thank you for your suggestion.  The thing is I need to design the heating system now, AS IF I've done whatever I can within my budget to seal the envelop of the house.  I won't be able to do actual test because I need to design then run electric and plumbing before insulating.

My plan for insulating the envelope:

-close holes near sil and in attic
- insulate 2x4 exterior walls with blown in cellulose or demin and, where open, r13 bats, followed by 5x8 drywall
-insulate attic with 12 inches of blown in cellulose
- insulate basement with R20 bats
-insulate ceiling of 1st and second floor with blown in insulation
-all new replacement and in some place new construction windows  (on south side use glass with higher solar heat gain)

The building is approximately 6000 square feet

Each unit is about 900 square feet the remainder is hallways.

I do have the option of tearing off the 2nd and 3rd floor ceilings but unless I get a huge efficiency (radiant possibility plus better insulation) I dont want to do this.  There's really nice one inch thick clay plaster on the ceilings. 

The heating should be zoned in three for each unit.

If anyone has suggestions for how best to seal this building or recommendations on best hydronic heating for my situation appreciated!!

Some questions:

Where is the building located?

How is it currently heated?

Does each unit have it's own electrical service?

How do you intend to write the leases with respect to utilities and operating expenses...i.e., who pays what?

Are there any local regulations regarding utility metering (i.e., heating water) by the landlord (as compared to a utility)?

Bruce

Thanks for your reply Bruce.

Where is the building located? Jersey City, NJ

How is it currently heated? No heat.  The building's been abandoned.  The previous system was one of natural gas space heaters.   Natural gas service by PSE&G.

Does each unit have it's own electrical service?  Yes, they will.

How do you intend to write the leases with respect to utilities and operating expenses...i.e., who pays what?  That's open still, but I'm leaning toward everybody paying their own, sinse this is about the only this that inspires the average person to conserve!  Typically landlords pay the building's cold water use \and tenants pay electric and gas (for DHW and heat).

Are there any local regulations regarding utility metering (i.e., heating water) by the landlord (as compared to a utility)?  No.

If it's plaster & lath in OK condition, dense-packing cellulose done from the inside works fine. Dense-packing will dramatically reduce air infiltration through the walls and adds thermal mass to the building, and will only require 1 hole per stud bay to patch per floor.

There is NO payback on radiant (comfortable, yes, efficient, sometimes, but economical from a fuel savings POV, not so much.) To be able to run high efficiency boilers, designing it with sufficient baseboard for to deliver the heat at 140F peak water temps (design-day, coldest hours of the heating season) and using the boiler's outdoor reset function delivers better than 90% true efficiency, and will be quite economical up front. If there's sufficient wall length to be able to do it with 125F water & baseboards it'll deliver better than 95% using outdoor reset control.

A single boiler & indirect water heater will be cheaper than 6, and the heat load for any single unit will likely be small relative to even the smallest condensing boilers, but it will be difficult or impossible to meter them separately if you go that route. A single larger boiler using a "reverse indirect" /heat exchanger like the( made in NJ) ErgomaxE44 (or it's Everhot or TurboMax cousins of similar size) would be able to handle the DHW load for 6 units fairly easily. Whether or not you'll want to use it as the heating system buffer depends on what your heating system water temps end up being. If possible, using drainwater heat recovery heat exchangers can boost both DHW output performance and save fuel. Using it as a heating system buffer means you're limited to ~90% efficiency with a modulating condensing boiler but since you're micro-zoning it into 3x6=18 separate zones, it'll at least DELIVER that efficiency, whereas you'd need to add separate buffer mass to most of the micro-zones to get optimum efficiency out of it even if you used 6 separate boilers. Alternatively a separate boiler to serve DHW with a reverse-indirect, and a outdoor-reset controlled buffer/hydraulic separator for the condensing boiler on the heating system could get you down to two boilers, and run at somewhat higher efficiency. Sizing the boilers properly for the true loads is HUGE in terms of being able to maximize the system efficiency. Many are oversized 2-3,even 4x for the whole building's heat load, then trying to serve a 1/18th of the building the thing is constantly cycling on/off, blowing away valuable heat with every start & finish flue purge. With a 50-100gallon buffer tank to work on it'll average the zone calls out, and the boiler will cycle far fewer times.

This is an issue whether you have a single boiler whole-building approach or a 6-boiler/3-zones per boiler approach. The latter can still work at 90% efficiency with a single wall-mounted ~50-60kbtu/hr condensing boiler + indirect-fired hot water system per unit.

Don't ignore the basement/foundation- sealing and insulating the band-joist & sill and the wall at least down to the frost line will reduce the stack-effect infiltration significantly. Make that basement as absolutely air-tight as possible, since it can be as much as 20-25%% of the total heat load of the building if unsealed & uninsulated. This will have a much larger impact on the building's fuel use than solar hot water.

No matter whether it's mid-efficiency cast-iron or condensing boilers, the lowest possible operating temperature results in the lowest fuel use/highest efficiency. If going the cast-iron route, mid-efficiency boilers should be sealed-combustion/direct vent types whenever possible for both safety & as-used efficiency. (If you're using heated air as combustion air, it's inducing higher infiltration and blowing away 1-3% of the heat, a factor not measured in an AFUE test.) Even for non-condensing units you'll save roughly 3% in fuel for every 10F you can drop the water temperature down to a lower limit of ~140F (below which you have to be very careful to protect the boiler from condensation damage to the heat exchangers). In the bad old days systems were designed for 160-180F water to save on radiator area, but with high-output baseboard and panel radiators rare is the system than actually NEEDs 180F water, even on the coldest hours of the year. The radiation has to be specified room by room, but you can usually get to 140F pretty easily in mid-atlantic type of outdoor design temps.

Separate blower-door tests on the different units will likely stop the bulk of the whole-building's air infiltration, but once that's been done the most economical extent, if there is a common entrance & stairwell, etc, run a blower door test there as well.

Solar preheat to the building can work, but would require a lot of plumbing for separate feeds to the distribution plumbing for hot & cold water, unless you take the single reverse-indirect approach and run it in series with the reverse indirect, and between the drainwater heat recovery and the reverse-indirect, if you go with drainwater heat recovery. If it's all ahead of 6 separate hot water heaters, the benefits reaped will be very uneven between users (those who bathe in the afternoon/early evening will use most of the solar heat, those who bathe in the AM get squat), but that's a separate issue.

I'm not sure if there's an easy solution to peops opening windows in winter, but with 3 zones per unit with their own thermostats it's a far cry from the typical whole-building central steam heating systems where some folks are roasting so they open the windows, causing negative air pressure to cool off the units on floors below, etc. That's not to say they WON'T open the windows, but they won't have to in order to stay comfortable.

Given that flow and temperatures are fairly easy to measure, why "difficult or impossible to meter them separately", ie,  measure BTU delivered to each tenant?

If you are going to meter utilities to the tennants, which you should, why would you install advanced systems with longer paybacks.

I can understand ones own home, but you are talking about taking an investment property and making it a worse investment.

If each unit will have a separate electrical service, have you considered mini splits for heating and cooling?  I don't know what possibilities, if any, there are to run ductwork, but it may be worth considering.  They are quite efficient until it gets really cold.  You also have the bonus of offering AC, although it may not be important to you or the tenants.

If you do go with a boiler and want to meter each tenant separately, you can do this reasonably inexpensively with flow meters and a weblogger (see the geothermal forum and search for weblog).  The concept here is that you want to allocate 100% of your heating utility costs when you are 100% occupied.  Assuming your primary fuel will be gas, that cost is easily identified.  If you want include the cost of pumping, it adds a bit of complexity and and another weblog point.   You could even add make up water and the cost of any water treatment.  You take all the costs you want to include and bill them proportionally to the tenants based on their metered use.

They do make BTU meters, but they are expensive and you don't need them....and then how would you calculate the cost/BTU?

The important point is that you will need to describe this utility billing structure in the lease.  The reason I asked if there are any regulations govening tenant utilities is that in some places landlords are not permited to "sell" or "re-sell" utilities.

Office building leases are usually "net", meaning that the tenants pay a base rent plus operating expenses which are either metered or billed pro-rata based on the rentable area.

Bruce

Posted By greentree on 08 Feb 2010 08:33 PM
If you are going to meter utilities to the tennants, which you should, why would you install advanced systems with longer paybacks.

I can understand ones own home, but you are talking about taking an investment property and making it a worse investment.

Exactly.

But if it's a "heat included" deal you can charge more rent, size the radiation & water temperatures with very small margins such that it won't keep up on cold nights with the windows open, use half the fuel of the typical multifamily heating plants, and it can still be a good deal for tenants and landlords alike.

You might be able to get away with a bunch of minisplits in this location but it's by no means a no brainer, and the upfront cost would be quite a bit more than a 1-2 boiler (or cogenerator) heating plant solution.  Electricity rates are significantly higher than the national average, and the average low temps Dec.-February are below where most are kicking into resistance heating back for hours on end nearly every night. Separate ~80% combustion-efficiency gas combi heat/hot water systems would be cheaper to run, with similar up-front expense.

But clearly the decision to combine or split heating systems has to be made early.

What about air conditioning

Thank you for all your responses here. 

I'll looking into the feasibility of the flowmeter for central heating plan option. But I am leaning away from the idea of administering the system myself.  

So. it's looking like 6 separate systems choosing between:

 6 boilers in the basement on a closed loop with radiators and baseboard plus a tankless heater in each unit's utility closet for dhw. 

or

6 boilers with indirect fire HW heaters in the basement

or

6 combi boilers in the basement

My budget is 4-6k per unit for the heating system. 

Can anyone recommend a configuration based on my budget?

Any thought on a reliable boiler product in my case (50/60kbtu)? 

Dana or others: would a solar (6 collector array) and/or wastewater pre-heat be possible with any of these options?  (If I do do solar I will need to figure out some way to recover that cost...  I know its not a great investment in my case, but I'm really amazed by the solar thermal technology and if I can afford it want to inspire others to take advantage...)

Does anyone have recommendations on radiator brands/types or the benefits of radiator vs baseboard?

Also Dana, in insulating the basement, were you recommending to dig down on the exterior of the building ("at least to frost line") or were you referring to insulating the interior of the stone foundation? 

About ac I am looking at those split models, but not considering them as a heat source. 

Thank you all!

One more idea for a system:

a solar tank plus a large tankless for all the building's hot water.  We'd pay for tenant's hot water, charge a bit more rent and recoup some of our investment in the solar thermal. 

The gas going to the boilers would be sub metered and the tenants would pay for that gas.

This would have the added benefit of avoiding the "no heat or hot water" problem...and would reduce the number of machines we need by 5.  

Maybe this is the best option?


Best,
Bisseti

Posted By Bisseti on 13 Feb 2010 11:50 AM
One more idea for a system:

The gas going to the boilers would be sub metered and the tenants would pay for that gas.

I think submetering gas will likely be problematic from a (economical) technical standpoint. 

Can your utility provide separate meters and separate services for the tenants....same as electrictricity?  What do you do for heating the common areas?

How active (or passive) do you want to be in the management?

Bruce

For $6K/unit you should be able to get a sealed combustion side-vented 85-86% efficiency ~60-70MBH unit that fits in a closet and a 30 gallon indirect for hot water + a single zone balanced-radiation baseboard. (Something like the smallest in the Burnham SCG series or Weil McLain CGS series.) If you start breaking it up in to micro-zones it adds another circulation pump valve & zone relay or zone valve and some complexity to the control/plumbing, and it'll short-cycle for sure.

For closer to $4K/unit you can probably get a ~80% combustion-efficient Bradford White Combi-Cor( M-2-C-TW-50T10BN or M2-C-75T10CN, depending on how much hot water you'd need) and micro-zone it. The thermal mass of the tank keeps it from short-cycling, and it'll be no less efficient than a standard tank during the summer (mid-50s for EF ratings.) There may be code-issues with combis in rentals in some areas, not sure if that applies to NJ.

If you design the radiation to deliver design-day heat at 130-140F (typically it means about 50% more baseboard) the additional upfront cost won't be much, but it'll save 10-12% on fuel relative to a high temp system. Cast iron radiators or flat-panel Euro radiators are more comfortable but are outside your cost constraints.

For insulating the foundation, if it's flat enough you can use rigid-board XPS, but on many stone foundations it's easier to use closed-cell spray foam insulation, up to 2". The below-grade portion needs to be able to dry toward the interior, which limits you to ~R10-R13, but that should be fine in that climate zone. It then needs at least 1/2" of wallboard or similar as a thermal barrier to meet fire code. A steel stud 2x3" studwall 24" o.c. on the interior works.

Drainwater heat recovery on the main drains, with the potable side in-series with the water feed to the units works. It'll be a grand or more per heat exchanger (installed), but if drains are commoned in the basement you can feed more than one unit with the output. The output of the heat exchanger will make the cold water coming in more like room-temp when someone is taking a shower, but it'll have better energy- return per $/investment than solar. If it's more than one unit per heat exchanger be sure to pay close attention to the specs for pressure drop with flow (some are better than others. PowerPipe looked better in that regard than the competition when I was looking, but it's a moving target- the industry is still innovating- they have competition. ) As single heat exchanger will typically return 20-40 therms/year per showering person, and if the plumbing location and water pressure issues work in your situation you could probably put as many as three units on a single heat exchanger. At higher flows the return efficiency drops, but doesn't fall off a cliff. (If it gets 50% heat recovery at 2.5gpm flow, it'll still be 40%+ at 8gpm.)

Bisseti here,

It's been a while since I posted to this thread, but an update if anybody is still looking at this.

Heat: I'm now looking at paying for heat for the 4 apartments with a central high efficiency boiler. I'm wanting to go for a solar h20 system with 6 to 8 tube collectors. I'm not sure it makes sense for me to think about that water in the heat equation. I'm trying to figure the sensible equation between the solar tank, the boiler/combi, hot water heater, with the obvious fact that we have the least solar in during the heating season. Looking at low temp rads (150) and baseboard (180). For the 2 commercial units I'm looking at HVAC systems on their own meters.

Doing 3.5" of open cell spray foam on the outside walls, the roof with 5" of o.c. on the deck and 2" closed cell 3lb above the deck.

Any suggestions on the boiler / domestic / solar questions?

Posted By Bisseti on 23 Mar 2010 10:33 PM
Bisseti here,

It's been a while since I posted to this thread, but an update if anybody is still looking at this.

Heat: I'm now looking at paying for heat for the 4 apartments with a central high efficiency boiler. I'm wanting to go for a solar h20 system with 6 to 8 tube collectors. I'm not sure it makes sense for me to think about that water in the heat equation. I'm trying to figure the sensible equation between the solar tank, the boiler/combi, hot water heater, with the obvious fact that we have the least solar in during the heating season. Looking at low temp rads (150) and baseboard (180). For the 2 commercial units I'm looking at HVAC systems on their own meters.

Doing 3.5" of open cell spray foam on the outside walls, the roof with 5" of o.c. on the deck and 2" closed cell 3lb above the deck.

Any suggestions on the boiler / domestic / solar questions?

By adding length, baseboard can be run at almost any temp, even though the typical headliner specs for it's BTU/hr- per-foot are often what it'll deliver at 180F.  By adding ~50% in length it'll deliver the same amount of heat at 130F.  Baseboard is cheap- less than $15/foot.  If you can get it to deliver design-day heat at 130F you could be in condensing mode with a mod-con boiler nearly 100% of the time.  Otherwise, a right-sized mid-efficiency cast iron beast, properly buffered & controlled can deliver your 150-180F water with 82-86% efficiency.

Buffering the heating system with a single ~35-50 gallon high-output reverse-indirect hot water heater (like an ErgoMax E44, or TurboMax 34 or 44)  maintained at a minimum of 120F  would work seamlessly with a solar tank in series preceding it.  Temp may be controlled with an outdoor reset control to higher temps as required by the heating system.  But 120F would be the temperature floor- if your heating system can deliver design day heat at temps lower than 120F a different topology would be more efficient, but a single reverse-indirect run as a seperate zone would still be the preferable backup to the solar, and the solar tank should be piped directly to the reverse indirect untempered, with the only tempering/mixing valve on the DHW at the output of the reverse-indirect.  With the buffering in place, whether you're using a modulating condensing boiler or something else, the number of burn cycles on the boiler are minumized, saving in both efficiency & maintenance.  The zones to the separate units can then all sip heat off the tank.  A crude schematic of what a system like that (without the solar portion) looks like lives here.

If it's possible to plumb a drainwater heat recovery heat exchanger in ahead of the solar storage tank, the economics still make sense if it's a single main-drain serving all 4 units.  If it can't be also plumbed to both the cold water feeds to the units + the water heating path, at least plumb it to the cold-water feed of the tempering valve to get at least 40% heat recovery out of a 50%-rated heat exchanger.  (The potable flow volumes would be too low to be efficient, if the reverse-indirect &/or solar tank were at 150-180F but mixing in city-water directly.  Mixing down with heat-recovery output to 120F at the output of the indirect, the flow of a 2.5gpm shower would be ~2gpm through the heat exchanger whether the indirect was at 120F or 180F.)

If the units are much further than 50' of plumbing from the main water heater, small-6-10 gallon electric tanks in the units might be in order. If they're receving 120F water on their "cold" input they'll never turn on,  but small draws of hot water would waste a lot of water (and heat abandoned in the plumbing) getting the hot water to the taps.  The electric tank saves them from having to wait for hot water, and will have some duty cycle for a series of small draws, but with anything like a shower or tub draw it'll turn off as soon as the hot water from the solar/boiler system arrives.

To figure out what size boiler you need, do a Manual-J or similar heat-loss analysis of the building as it will be after the insulation/window upgrades, etc are in. If you don't oversize the boiler's output by more than 15% per manual-J the boiler will pretty much meet or beat it's AFUE numbers.  Most mod-cons have heat-purge type controls, but if you go cast-iron that's usually a retrofit.  If you're using a cast-iron boiler and an insulated buffer tank the fuel savings from heat-purging the boiler into the buffer are substantial.  See system #3.

Hi Dana et al.

On the question of heating the 4 apt in Jersey, I've "boiled" it down to either the central boiler idea or an instant wall mounted in unit boiler/dhw for each unit.  (the stores are getting their own hvac, as I really don't know what kind of stores they will be...)

If a mod con boiler runs baseboard at 180 what degree of efficiency will I loose?  I can't seem to find any plumbers who have experience with low temp heat....

I've submitted a request on this site for help, we'll see where that leads.   

Posted By Bisseti on 01 Apr 2010 09:11 PM
Hi Dana et al.

On the question of heating the 4 apt in Jersey, I've "boiled" it down to either the central boiler idea or an instant wall mounted in unit boiler/dhw for each unit.  (the stores are getting their own hvac, as I really don't know what kind of stores they will be...)

If a mod con boiler runs baseboard at 180 what degree of efficiency will I loose?  I can't seem to find any plumbers who have experience with low temp heat....

I've submitted a request on this site for help, we'll see where that leads.   

The combustion efficiency achieved is a function of the return-water temp, not the output temp.  Condensing begins on natural gas burners when the return water gets down to ~125F or so.  Typical delta-Ts on radiation tends to be in the 15-30F range (and must be within the limits of the boiler's tolerance or extra near-boiler plumbing is required.)

The radiation temp requirements can be brought down from 180F to 120F by adding roughly 50% more radiation.  With baseboard this is cheap- just add  50% to the length at $12-15/foot but you may run out of wall space in some situations.

But since you only need 180F water on the very coldest 3% of hours in a heating season, using a mod-con's outdoor-reset control to lower the output temp as the outdoor temp rises means that you'll be in the condensing zone much of the time. Setting up the reset curve requires some post-installation tweaking, but it's not hard to get in a reasonable range.  When done right, with the boiler SIZED right for the peak loads, the boiler will run nearly constantly for much of the winter.  It's not hard to beat 90% efficiency with a right-sized mod-con retrofitted to a 160-180F baseboard radiation, and dead EASY to beat it on a newly commissioned system with extra length.

The issue you will very likely run into doing individual boilers on the apartments is that the design day heat loads are still lower than the output of the smallest mod-con boilers.  In that case, find the boiler that has the lowest modulation point (the smallest Lochinvar Knight ~50MBH units may be the only ones that drop below 10KBTU/hr on low-fire, but it's a moving target- there may be others.)  The lower it can fire, the more condensing time you'll have and the fewer cycling losses, which all adds up to more efficiency.  If done as individual apartments, single-zoning the heating and using a standard indirect for hot water may be the cheapest/most-efficient.

Call the local distributors for condensing boilers, see if they can give you a reference for an experienced installer- it can make a world of difference in getting operating efficiency & system design right the first time.

A shorthand explanation of the condensing boiler efficiency curve.: At 150F return water temps NOTHING gets better than ~85% efficiency, but it rises slowly to about 87% as the return water temps come down to 125F. Below that it rises quickly- at 120F return water you get roughly 90% efficiency, at 100F return water you're at 94-95%, but it has to be ultra-low to get better than ~96% (possible some of the time, in radiant slab floors.)

AFUE testing is done with 140F output, 120F return, for non-condensing boilers (which would void the manufacturer's warranty if operated that way since some amount of condensation WILL occur and shorten the life of the boiler.) But an 85% AFUE cast iron boiler won't deliver much worse than 84% running at 180 out, 160 back- not a huge combustion efficiency performance hit. But operated at those temps, so would a 92% AFUE mod-con.

But there's more to system efficiency than mere combustion efficiency at the boiler. With retrofit controls, the output temp of a cast iron boiler can also be varied with output temp, which delivers more performance gains than mere combustion efficiency would explain. Standby & distribution losses fall when the boiler is at a lower temp, and the rule of thumb is that you save ~3% in fuel for every 10F you lower the temperature until you get down to the condensing zone (at which point combustion-efficiency climbs rapidly.) Designing cast iron boiler systems for low temp still counts, and if properly sized to the load, aren't terrible. But when they're 2, 3, 4x oversized the operational efficiency slides over a cliff. The modulating aspect of condensing boilers is as-important as condensing in keeping system efficiency up.