Staged investment in radiant heat

CapeCod

Just bought a 1.5 story cape cod (1952) where the attic has been converted to the master bedroom. Only have one bathroom so thinking of adding a second bathroom in the converted attic. To add bathroom would mean removing chimney whose only purpose at the moment is for venting the water heater. So i would potentially be in the market for a new water heater anyway Current heating system is a high efficiency forced air furnace that is from mid-eighties. The forced air does not do a great job heating the attic and it would be nice to add radiant floor heating or a towel warmer to the new bathroom so I was thinking about adding a radiator to the bedroom as well. I am not swimming in cash so I am trying to avoid this turning into a slippery slope of remodeling. At the same time I would love to completely eliminate the forced air and add radiant heat to the main floor some day. I have a lot of questions but will limit myself to one for now. Would it be feasible to add an "oversized" boiler now to accommodate heating the attic bedroom and bathroom and possibly an indirect water heater while keeping the option open to add another zone or two a few years from now to heat the rest of the house?



Appreciate any comments you have. I just stumbled on this site over xmas and It has been very interesting and addictive reading all the posts here. Thanks in advance and happy new year.

STEVEusaPA

Of course

First, please find a very competent installer, someone who knows radaint hydronics. Have them do a complete design which of course includes a complete heat loss. If you can go gas, you should go with a mod-con boiler, and indirect. All the near boiler piping can be done to accommodate the complete system and you can add on easier when your ready.

CapeCod

Would like "pre heat loss calc" advice

Of course I will work with a qualified contractor. I am an engineer but I also know my limits. I am looking for some general advice so I am better prepared to talk with a contractor. Suppose the heat loss for my number 1 priority of the attic is X. I want to add an additional zone in 3 years that would have a heat loss of 1.25X and a further zone in 5 years that has a heat loss of 1.75X.



Just want to know if I am thinking about this in the right way....I could:



1) install boiler sized for 3X future load but only use 1/3 of its capacity. Would it short cycle or would a modulating boiler alleviate that?

2) install correct sized boiler for current use and switch later. Probably not economically feasible.

3) is there a way to manifold two smaller boilers. Again seems to complicated and expensive.



Appreciate any comments. I don't want to waste contractors time and my money on heat loss calc if it is not worth it. I can always install electric radiant in tile of attic bathroom and use a booster fan to try to get more forced air heat upstairs and forget the whole thing.

Jean-David Beyer

Would it short cycle or would a modulating boiler alleviate that?

My guess is that it would short cycle. Modulating boiler would alleviate that, but not cure it. My boiler is about double the size it needs to be, but it is the smallest in the product line.There may be modulating boilers that go lower than 20%, but I imagine they are few. Remember you do not normally want to depend on modulation to get the boiler down to what you need on design day; you want it to get you down to what you need on the warmest day you use heat, and that is quite a bit less.



"is there a way to manifold two smaller boilers"



Yes. My W-M Ultra 3 can certainly do this. The problem you will probably have is that there will not be any mod-cons small enough to do it. I have a small (1150 square feet, total) Cape Cod and the smallest W-M Ultra 3 is 80,000 BTU/hour (input) and that is about twice what I need. If I could get any size boilers I want, I would get one 7,500 BTU/hour one and one 25,000 BTU/hour one. But in the interest of simplicity, I would get a 35,000 BTU/hour one.

CapeCod

thanks

OK, thanks...that is kind of what I was hoping to hear...a glimmer of hope.  I will be contacting someone soon to see if it is even in the ballpark of what I can afford.

Paul Pollets

Choices

Presuming you have nat. gas, there are several modulating "combi" wall hung models that will both heat the home and provide plenty of DHW for a home up to 2.5 baths, as long as there are no soaking tubs. The NTI and Triangle Tube companies make the appliances and the NTI has the ASME "H" stamp. Both separate the DHW from the heating water, so there's no risk of potable contamination. I like the NTI unit because of the ability to pipe it from top or bottom, and the very neat Honeywell "Sola" control. Either will allow future expansion and come with a max of 100K Btu output for heating. BTW, same burners and heat exchangers in either unit.

CapeCod

One more recommendation for the Triangle Tube

I went over my scenario with a local contractor and he also recommended TT....the Prestige Excellence with a small built in buffer tank.  This will allow me to replace my existing water heater and set the groundwork for converting the entire house to radiant heat eventually.  I only have one bathroom now but will add one more soon.  I think it only produces 3 gpm of hot water so having both showers going at once might be too much for it to handle.  Our kids are still young but I am thinking about going to a larger tank for more hot water reserve in the future.  Happy to hear many positive comments on Triangle Tube.

SWEI

good choice

...but you really should insist on a heat loss calc before you sign anything.



If you really think you will need more hot water capacity later a separate SMART indirect might be a better choice.  The price difference between the SMART 30, 40, and even the 50 should not be very significant when you compare total installed system costs.



The little tank in the PE110 is great for small houses - too bad they don't offer it with the 80k boiler.  Install a couple of good 1.75 GPM shower heads and it will go much further.  I'm really impressed with the Kohler K-10240, but there are plenty of choices out there now.

CapeCod

SMART indirect

Thanks for the advice....the guy actually added an option in the quote for adding an larger indirect tank although not from TriangleTube.  I was also thinking about getting a low flow showerhead...I put one in a few years ago and it was terrible but looks like there are some viable alternatives.

SWEI

showerheads

We're remodeling an old hotel and have been evaluating showerheads for about a year. That particular Kohler is really quite impressive - I never would have guessed it had such a low flow.  We tried others that performed almost as well, but didn't look anywhere near as nice (appearance matters far more in for hotel than at home in our case.)  It's not cheap, but there are many that cost quite a bit more and do not perform as well.



Switching from a PE110 to a PS110 (assuming that's the correct size) should offset a good chunk of the SMART cost.  Be sure the installer changes the aquastat out for the sensor (included with the boiler.)  And don't "allow some extra" for the DHW unless you have some kind of regular and huge demand.



Good luck!

CapeCod

should offset a good chunk of the SMART cost

The option to add the indirect fired heater was indeed relatively minimal compared to the total installation cost so I can only assume he substitued the PS110 for the PE110 as you mentioned.



Sounds like you are an expert on shower heads after your research.  While on the subject, do you know of a good handheld lo flow showerhead?  I looked on Amazon but couldn't find much...

SWEI

handheld showerheads

Grohe is probably the best-known maker of handheld and other configurations.  We had one in our Reno house that we liked.



Kohler does make a handheld 1.75 GPM version of this, p/n K-10298.  Haven't ordered hardware for our accessible rooms yet so I can't comment directly on it, but it is supposed to have the same internals and performance.



BTW, in a strange twist this apparently does not meet ADA requirements (working from memory here) which require a high and a low setting.  The K-10298 apparently meets the low flow requirement of the standard, but lacking the higher setting somehow means it does not officially comply with ADA.