Future-proofing puzzle

stick_house

Hi!
I'll try to keep this short.

I recently moved into an MA house built in 1912. The oil burner is cracked and needs to be replaced. With what though?

It's a 1300sq feet space, currently with some 10 old-style radiators retro-fitted for water instead of steam. I'm planning to gut the house in some 3-5 years, when I save up enough, and change all the plumbing, some room placements, install panel radiators, insulation, new windows... Essentially, to retro-fit the house in a very energy-efficient way. What do I get now, that would blend well with future plans? It looks like sticking to oil, despite all the disadvantages, is still the best bet for the area.

I am not from the US and at home everyone just has a brick house, a Vaillant and panel radiators as a standard. Looking at different brands and ways of going about heating spaces, rebate options etc is becoming overwhelming. What would you do in my place?

Steamhead

First thing to do is a heat-loss calculation of your house. I bet you find the current boiler is oversized.

If possible, add insulation to your top floor ceiling. Also the walls, if doing so won't cause moisture problems (talk to an insulation specialist for more on this). This will probably put you into a smaller boiler. You can run a "what-if" heat-loss calculation to see how this would work out.

Cast-iron radiators were used in hot-water systems when they were first built, as well as steam ones. They are one of the best heating methods ever designed. I wouldn't be so quick to trash them.

hot_rod

Future proofing to me is designing around a 120F or lower SWT on a design day. This opens you up to using most any heat source efficiently. Solar thermal, condensing boiler A2WHP, even a conventional boiler will be most efficient at low operating temperatures.

Load calc first, then see how low you could run the cast rads. Or panels if you prefer.
Download this free journal for other ideas.

mattmia2

Are you sure it wasn't originally a gravity hot water system rather than steam? Some pictures of the radiators with their piping and piping in the basement will clear that up.

Cast iron radiators and especially large gravity hot water piping has a lot of mass which solves a lot of efficiency problems with short cycling. If you can set up the water temp with an outdoor reset control that sets the water temp based on the outdoor temp and therefore the approximate current heat loss that mass just stays warm all the time constantly adding just the right amount of heat to the building. A perfect heating system would always be on modulating its output to match the load.

Like others said if your radiators are large enough they can use the low water temps where condensing boilers and heat pumps are most efficient. Even if they aren't, if the design is correct it will be more comfortable than modern systems.

Hot_water_fan

Will the gut allow for ductwork? Adding AC might be a valuable addition and could change the heating system easily. 

EdTheHeaterMan

Hot_water_fan said:

Will the gut allow for ductwork? Adding AC might be a valuable addition and could change the heating system easily. 

But you need a boiler today. If you do Ductwork in the future rehab, you can heat the ductwork with water to air coils. If you will be staying with cast iron or European panel radiators or even low cost baseboard. then the boiler you purchase today will need to handle the load as the structure stands currently. In the future the boiler may be able to fire at a lower firing rate. Many oil boiler have a minimum firing rate and maximum firing rate. My suggestion is similar to @hot_rod Bob's... Select the boiler based on your future use being smaller than it is now and therefore you can use a lower operating temperature. For Example:

Purchase a boiler that can heat the home on the maximum firing rate. In the future redesign, you can fire the boiler at the lower firing rate.

This illustrates that the FWZ 80 and the FWZ 81 are basically the same rating. if your current heat loss requires about 80,000 BTU, then I would select the FWZ 80, In the future you could reduce the firing rate to the lower BTU specification of the FWZ 60. To dot all the tees and cross all the eyes, you may even be able to have Velocity Boiler provide you with 2 different rating labels with the Block Only serial number. this boiler block will be under the same warranty and then you select the burner based on the load calculation. Then change the label to the lower firing rate once the upgrades are in place.

I might be able to facilitate that rating plate label if you are interested in using a Crown Boiler by Velocity Boiler works. Is there a Crown Distributer near you?

Same idea if your load calculation is 140,000 now and might be as low as 100,000 after the rehab. Purchase the FWZ 100 today and change to the lower firing rate after. This i one manufacturer I'm familiar with. There are other manufacturers that also have multi firing rates for a given boiler size.

Just a thought.

Mr.Ed

The Steam Whisperer

I agree with much of the above. Figure out just what the house is going to look like in terms of thermal performance once the rehab is done. Calculate your heat load based on this configuration. Then run a load on what you will need next winter. Going from typical 1912 construction to an (as an example) well insulated building with air tight drywall design will likely cut the peak load almost in half. I suspect with a home this small, you are going to end up with the smallest boiler model available. If you do need larger boiler now and then a smaller later, I would install the smaller. If your weather pattern is typical, you only need 60% of you boiler capacity for about 98% of the heating season. If you install the small boiler now, you will only run out of capacity to maintain comfortable temperature in the home maybe 2 or 3 days in the winter without the home upgraded. A couple of supplemental electric space heaters will get you through that cold snap or just bundle up a bit. Then when you're done with the renovation, you will have an optimum sized boiler.

As an example: My own 1903 Chicago home needed about 110,000 input gas boiler for about 2,100 sq ft of finished area above grade, 1500 sq ft basement, before rehab ( 175,000 was installed) , after rehab we will need about 60,000 btu/hr input. I'd put in the 60,000 input boiler and then rehab the heat loss down to the boiler size. As an FYI, the load of our current 1500 sq ft mostly rehabbed 1st floor and and basement requires only about 45,000 btu/hr input when it is -5F outdoors. We use under 200Therms of gas and about 230 KWH of electricity the worst month of the winter with our 30 year old 105,000 btu/hr input cast iron boiler.

Hot_water_fan

It’s April, there is no emergency. For a house that small, with anticipated upgrades, ditching oil and installing ductwork could avoid a boiler install, gain some more square footage, gain a cheaper energy source and gain AC. There’s no way to be energy efficient with an oil boiler. 

Jamie Hall

"There's no way to be energy efficient with oil" is a wonderful talking point. Pity it isn't true. What is true, however, is that if you can retrofit with heat pumps with a COP of at least 2.5 at your design temperatures, you can equal oil, so that may be an attractive approach as part of the overall rehab project -- either driving low temperature radiation or using ductwork.

The problem is that you have the cart somewhat ahead of the horse. You are planning a gut rehab (frankly, a tear down and rebuild might be more effective and possibly no more expensive, and would give the option of a substantial passive solar heat gain), so you will -- if it is done properly -- have a much lower heat load after you are done than you have now. But --you need heat now, not down the road when that work has been done. The problem of course is that investing in a heat source -- of any kind -- which is adequate for the present condition will result in a system which is ovesized and thus more expensive to purchase when the rehab is finished. I don't see a good way around that, but what I would suggest is probably the least expensive approach is the get an oil boiler which is suitable for the present condition, properly installed, This will give you more time to properly plan and execute the rehab, if nothing else.

hot_rod

If you are used to panel radiators in your other homes, you may, probably will not be happy with a forced air heating system. The quiet clean comfort of hydronic or steam is hard to beat. Usually fairly easy to retrofit panel rads with room by room control.

The decision is whether to include AC. I prefer ducted systems, a mini split or two may be an option?

Hot_water_fan

Agree with @hotrod, this is the best time to decide on AC (we’re talking future proofing after all!). If you go that route, a heat pump can do double duty. It’ll be your decision whether to keep hydronic heating, which could also be an air to water heat pump or a boiler of some sort. 

@Jamie Hall in 2022, it’s a stretch to claim that a oil boiler, with a max efficiency in the 90% range is more efficient than a heat pump, especially with the heat rates on new combined cycle plants. The math is the math. 

There’s some merit to considering skipping a full blown energy retrofit, especially for a home that size. I imagine the current heat loss isn’t outrageous, so it could be a cheaper path to only do comfort related air sealing/insulation plus heat pump. Insulation reaches diminishing economic returns quickly, dependent on climate, energy costs, and installation costs of course. I’d focus more on comfort and let a cleaner heat source handle the efficiency / environmental gains. 

Jamie Hall

I completely agree that a heat pump, so long as it is running at a decent COP, is as -- or more -- efficient than oil. In fact, I just installed 50,000 BTUh worth of minisplit heat pump in part of Cedric's home, partly for that reason and partly to give that tenant more control of her heat (she's older)(interesting exercise -- the National Park Service requirements are very strict!).

My only point is that neither heat pumps -- in any form -- nor oil boilers nor passive solar nor any other technology is the single best solution for a given situation, and it is important that we all keep all options in mind.

Hot_water_fan

@Jamie Hall you’re always reasonable! I meant in the context of this post, an oil boiler for water (steam is different as you well know), will be less efficient. There will be exceptions out there. 

The Steam Whisperer

I don't know the efficiency of the overall "grid " for oil, but when looking at natural gas and electricity, Assuming an 84% efficiency boiler and a grid efficiency of around 90%, this equals an overall efficiency of about 76%. Assuming an average COP of 2.5 for a heat pump and the electrical grid efficiency is about 35% that give you an overall efficiency 87%. Then factor in the life of the heat pump( maybe 15 years) versus the boiler (probably 25 to 30 years) and you probably end up with about the same life cycle efficiency. If you don't believe the electrical grid is only 35% or so efficient, the DOE Energy Star program uses a multiplier of about 2.5 for electrical energy savings in btu's versus natural gas savings in btu's. Using less electricity is 2.5 times more effective than using less natural gas.

Hot_water_fan

@The Steam Whisperer I don’t know the utility of comparing a brand new boiler to old gas plant? At the margin, a new boiler underperforms a new gas plant and it’s not particularly close. 

That there’s no oil electric grid only proves the point that it’s ill-suited for these kinds of applications. 

hot_rod

What gets missed often with efficiency numbers is the actual operating condition.
Buildings are at design condition for a small % of the year. So whatever published number you look at for efficiency is under ideal steady state operation. Brookhaven lab studied this. Oversizing really kills efficiency numbers. Short cycling kills those published efficiency numbers. Dirty boilers effect the numbers.

So the mod con boilers, even when not condensing, stand a much better chance of keeping efficiencies high, as they modulate to the ever-changing loads. With properly dialed in ODR they can and do run steady state for much of the heating season. Micro loads tend to hamper steady state, even with modulation, to a degree.

Still, the bottom line is always the structure It dictates the operating condition of the boiler.

The Steam Whisperer

A new gas plant may hit 40% efficiency if you're lucky....measuring btu's of gas burned versus btu's of electricity out. Electrical generation is very inefficient and you lose a little bit more out on the power lines. That's why combined heat and power was so popular and is still an extremely efficient alternative to using heat to just warm buildings and not turn electrical turbines.

Operating conditions are the other big factor. Modulation or step firing is a huge gain that has long been proven to boost overall efficiency of the system..not just the boiler The old high mass water and steam systems ran with a natural outdoor reset with long steady burn times and long off times....providing excellent efficiency. Reset helps prevent hot air stratification, making the building lose less heat.

Upgrading the thermal performance of a building saves in 2 ways..... You obviously reduce the amount of heat needed to keep the space warm at a given outdoor temperature, however, you also reduce the length of the heating season for most buildings. People living in the home , lights, cooking, bathing all generate heat. Solar gain can add alot too. All this heat can keep the heating system off in moderate weather in a well insulated and air tightened building where a looser building the heating system will need to turn on earlier in the season and run later.
Building performance should be the first focus.

Hot_water_fan

https://www.eia.gov/electricity/monthly/update/archive/october2020/

51% is the average efficiency for CC installed since 2015. The newest generation is very impressive. 

Anyways, the AC decision drives the future proofing conversation IMO. 

leonz

stick_house said:

Hi!
I'll try to keep this short.

I recently moved into an MA house built in 1912. The oil burner is cracked and needs to be replaced. With what though?

It's a 1300sq feet space, currently with some 10 old-style radiators retro-fitted for water instead of steam. I'm planning to gut the house in some 3-5 years, when I save up enough, and change all the plumbing, some room placements, install panel radiators, insulation, new windows... Essentially, to retro-fit the house in a very energy-efficient way. What do I get now, that would blend well with future plans? It looks like sticking to oil, despite all the disadvantages, is still the best bet for the area.

I am not from the US and at home everyone just has a brick house, a Vaillant and panel radiators as a standard. Looking at different brands and ways of going about heating spaces, rebate options etc is becoming overwhelming. What would you do in my place?

=================================================================

So, you have a 40 by 30 bungalo as we refer to them here? It is very difficult and expensive to change steam radiators to hot water service. Do you have a basement where the boiler is?? It would be great to know if there is or was an open to air expansion tank in the attic or if the plumbing for one was left in place and visible.

Like I said before pictures would help us a lot especially if the heating system was ruined before you bought the place.

Pictures would help us a lot with this.

You have thermal mass in the radiators to take advantage to heat your home with a very low temperature water of 170 degrees Fahrenheit (77 Degrees Celsius) and it would be a real shame to see them removed when all they may need is cleaning in the total scheme of things as you have a huge amount of useable heat storage in the water capacity of the radiators and the piping that will just shed its heat slowly.

The Steam Whisperer

Hot_water_fan said:

https://www.eia.gov/electricity/monthly/update/archive/october2020/

51% is the average efficiency for CC installed since 2015. The newest generation is very impressive. 

Anyways, the AC decision drives the future proofing conversation IMO. 

I believe you're reading the graph wrong... 51% is the capacity factor. Heat rate is 7400-7600 btu/ kwh.
That works out to 45.5 % efficiency, which sounds like the plant can reach when running at optimum capacity. So plant efficiency has improved, that would put the efficiency of a new plant with a good grid probably around 42%.

yekimouse

Nah, Hot Water Fan is correct the heat rate for the newest plants is listed in the second to last paragraph:

In contrast, the low 6,654 Btu/kWh heat rate of NGCC power blocks installed since 2015, which represent 11% of all NGCC capacity, helped drive the capacity factor of this group up to 63%.


To express the efficiency of power plant as a percentage, divide the equivalent Btu content of a kWh of electricity (3,412 Btu) by the heat rate -- so 3412/6654 = 51.2%. Since they're so efficient, they're used more frequently, hence the higher capacity factor of 63%.

Modern CC power plants are a marvel and are nearing the theoretical efficiencies -- most heavy manufacturing companies (GE/Mitsubishi/etc) have announced/produced >60% efficient turbines which is something like 90% of the theoretical carnot efficiency.

E.g: https://www.ge.com/gas-power/resources/articles/2018/nishi-nagoya-efficiency-record

The Steam Whisperer

Whoops, that was for the units built between 2000 and 2015. It's nice to see that real improvements are being made. However, in the big picture 51% efficiency is still sad with about 47% at the consumer user point. They could probably get the efficiency well over 100% if they did CHP with the units, but that would require community wide planning like we used to do in the U.S.

In_New_England

How about installing a modulating condensing gas boiler that will serve as backup for future heat pumps after the rehab?