Antique Under-Floor Radiator Issue
Hi all —
I’m a remodeling contractor from Maui, HI. I’ve been remodeling mostly condos for about ten years, and I come back East every Thanksgiving to see my parents and whoever might show up for the holidays. So, here I am in my hometown of Boston, just in time for some cold!
My parents have just replaced their boiler and as my dad was explaining the eccentricities of their heating system, I began to wonder how it could be improved. My Parents’ house was built in 1913 and has a forced hot-water system (previously most likely steam). The first floor has several under-floor radiators that are located in asbestos-insulated duct boxes in the basement. The problem is this: These boxes are connected, via old, rusting galvanized duct work, directly to intake registers outside of the house. As the radiators heat, the rising heat pulls in fresh air from outside (convection?). The problem is, of course, that a tremendous amount of energy is expended heating the freezing cold air enough to keep the house comfortable.
It seems to me that the old duct work should be reworked so that it feeds filtered return air from either the basement or main house to the radiators, thus reducing the radical temperature difference between the heated air and the intake air. I think the house is leaky enough that there doesn’t need to be make-up air engineered into the system, but I’m not sure.
Does anyone have any experience in this area? What can be done to make this kind of system efficient and less wasteful?
Looking forward to any assistance.
-Pete
Replies
I tend to agree ... pull air from the basement and up through the radiators. Allow nature to ventilate the rest. You may need to have a return air back to the basement to promote free air flow. Never heard of this system you describe ... just when I thought I'd seen/heard it all ... never fails ... run into something new.
Seems like there must be a reason for pulling in outside air ... unless in 1913 ventilation was important for some reason (smokers, smoke from fireplace? cooking?).
I had never heard of it either, and neither had the heating contractors who have worked here. It's called indirect heating. A guy on another forum sent me this link:http://www.heatinghelp.com/heating_howcome2.cfmwhich provides a huge amount of information on the system. It's pretty neat, but really outdated. He's got a book I just ordered.In a nutshell, large homes owned by wealthy people installed these expensive types of systems because they thought that stale air promoted disease. This was the first system to utilize duct work and fresh air. The formulas in the link are pretty cool. They had to size the indirect radiators up by 75%!! Anyway, today it's like watching dollar bills float out the (original) windows.
Neat!
Interesting stuff. I'd still think a little about how the air gets to the basement to come up through the radiator ... normally referred to as return air. A passage of free flowing cooler air to the basement will ensure that a lot of air passes over the radiators and more efficiently heating the house. Something to consider, anyway.
Definitely interesting. My folks seem resistant to spend any money correcting the problem. I think they're gonna leave it for the next owners. This house needs MAJOR work to make it energy efficient and to even approach green construction.Nevertheless, I have been thinking about what would utilize the warm air already in the home. I think installing return grills in the floor of the first floor that attach to a filtered air handler would be a start. Even better, though, would be a register in the ceiling of the third floor above the open central stairway that routes the air to the indirect radiators via the same type of air handler. That would probably create a better overall flow through the house. I think the problem might be that since the existing indirect radiators are 75% larger than necessary (according to that link), the balance of the system might be thrown way off. So it might be hard to have the three floors all comfortable at the same time.What do you think?Tear it all out and start again??-Pete
tear it out? ... my reaction is ... no way. Keep in mind, I do not have your detailed perspective/knowledge on the matter. Not sure you need a fan/AHU to increase air flow ... just a gentle nudge here or there w/ some reconfiguration/improvement of some elements to eliminate the bad and improve on what is there.
I don't think an oversized system is necessarily a problem. Since this is hot water heating, you should be able to balance/rebalance the system as you eliminate the excess ventilation. Hot water heat can be 'tuned' to the load by simply reseting the supply water temperature ... a common practice in hot water systems (particularly in commercial applications). For low loads (e.g. w/out ventilation and/or milder outside temps), you allow the supply water temp to drop.
You may be able to further fine tune the system with e.g. control valves on the radiators (not sure of your loop configuration). You could then put a stat in each room or one for a series of rooms to balance the comfort in the house.
If you have no reason to believe that you have problems with your hardware (i.e. piping and coils) in terms of corrosion or such, you could have a workable system with some changes and fine tuning that retains the 'old world charm' while updating the efficiency of the system. Again, keep in mind, my very limited familiarity w/ the details of what you are actually having to deal with.
I tend to take the approach ... if it is still usable ... use it! Improve it. Make it work.
There was a big movement in California to do the same thing, except out here it involved getting fresh air by using sleeping porches, and sleeping outdoors in all weather. Thought to to be the cure for all respiratory disorders. Big need to bundle up in the winter, but sold a lot of rolling beds. As a classic example, most of the second floor porches on the Gamble House in Pasadena, for instance are sleeping porches. They were very common in almost all houses above small bungalows or courts in the early 1900's.jose c.
--
"Though I don't think" added Deep Thought "that you're going to like it."
It's funny how the fresh air issue sort of disappeared for many years. There's definitely something to it, and now there are many articles on indoor air quality especially because we are sealing houses up so tightly and trimming them out with poisonous finish materials (MDF, carpet, vinyl, etc.).We need to return to using safe, healthy indoor materials and providing adequate fresh indoor air. This time, though, it needs to be done in an energy efficient manner. No more cranking the heat up and opening a couple of windows for ventilation!This heating system definitely had the right idea.
Aloha Pete -
No, the problem is this: You have asbestos in proximity to an air duct system in a house. That is their primary problem and it needs to be rectified.
You are 100% correct about fresh air as a hedge against disease - this is why radiators in houses between certain years (say 1915-1925) were so oversized - they mostly left the windows open year round.
The old duct work, if you even keep the heat distribution system, should be completely replaced and the asbestos remediated.
Jeff
Edited 11/22/2008 12:40 am ET by Jeff_Clarke
Thank you guys both for the responses. I'm pretty sure we won't be tearing the system out. I'd like to see the air recirculated without bringing in fresh cold air. Thinking about trying to hire a heating engineer to take a look and spec something. I agree that the asbestos in proximity of the ductwork is a horrible combination. I think no matter what is done, that ductwork needs to be removed.Ironically, My parents have owned this home for 29 years, and never really done much to the heating system. It's just in this day of energy awareness that I've really had a good look at what's going on there. They had the asbestos in the basement sealed, but now that I think of it, that only protects the basement air. There's a good chance that they've been circulating asbestos from the inside of the ductwork forever. They've had indoor air quality analysis done and found it to be safe, but I don't know how recently.
Without being there, I would say the asbestos in not being moved around. One thing in its favour is it is tough. Undisturbed, it just stays there.
That seems to be the case. They've had a number of mishaps with that asbestos over the years, though. A couple of years ago, they had a central air conditioning system installed. The installers drilled through the asbestos-covered ductwork to attach flex-ducts to them. Asbestos dust got all over everything in the basement, and my folks had to have an asbestos remediation team clean up down there which was expensive and invasive. They threw out the couch of my high school years -- you can imagine the things that once happened on that couch.Anyway, when there's no construction and the asbestos is left alone, it's fine. I may suggest to them that next time they have any work down there they remove it to avoid that situation in the future.