Home Radiator Reflector

Radiator Reflectors / Radiator Heat Reflectors
As is typical, I've already made and installed mine (see step by step below), and now that I'm writing about these later, have now done a lengthy search on the Web to get my facts as straight as possible for you all. What I've found is much controversy concerning the effectiveness of radiator reflector panels. What we are talking about here is some form of reflective material (sometimes with insulation too) placed on the wall behind radiators.


If you want to skip the controversy and technical reading, and just want to make them like this, then skip to the lower part of this article and see "Here's How I Made Mine for my Big Steam Heat Radiators" (Note: click on photos to enlarge them)

Those promoting reflectors suggest that heat from the back of the radiator is lost through the wall behind and then heats the great outdoors. The controversy lies in how much energy savings can be achieved through adding these types of reflective/insulated panels. Some say very little while others say a great deal.

Here's what you'll find from a Google web search:
1. The UK sells lots of radiator reflector foil and other prefab products
2. The US sells one prefab solution that I found after about 10 Google search result pages.
(UPDATE 10/30/2009: Reflectix, Inc. now advertises it's foil faced bubble material, which is the stuff I used as a solution, to go behind hot water radiators, they say nothing about steam radiators. It can be purchased at HD. Here's a link to their short article on easy installation, using double-sided tape, Velcro, and so on to adhere the material. In their short introduction they don't actually say anything about energy savings, they just say, it will "increase the heat transmitted to the interior of a room..." "This will result in a more comfortable room at a lower thermostat setting.")
3. Novitherm (Canadian) sells these prefab radiator reflector panels
4. Gaz M├ętro (Canadian gas company) offers them for free as part of their Energy Efficiency Fund. See their promo brochure here.
5. Quite a few sites mention them quickly as energy savings tips
6. Online forums debate about their effectiveness and how to make them.

Radiators transfer heat to your room through "Radiation" and "Convection". Basically, "radiation" is the transfer of heat from one object to another through space when they have a direct line of sight to one another. Convection is the transfer of heat through fluid (air counts). The hot air rising above your radiators is doing so because of the heat differential of the hot and cold air in the room, and the hot air (heated by convection) is rising.

Is There Any Proof that Reflective Radidator Heat Panels Work?
In my quest for statistical proof of the benefit of radiator heat reflecting panels, I found the sources on the Novitherm website to be the most complete and compelling. I encourage you to read their site, but mostly the three independent studies presented there, under the section "case studies". If you don't have the time, the general outcome of the performance of their product indicated a 10% energy savings in each study. The studies where not perfect as there are so many variable that factor in, such as people opening their windows and so on. But all in all it seems to be proven that these things work.

In one of their reports Novitherm seems to suggest that their product can be painted with no effect on performance. Studies have not be done to confirm that, but as pointed out by the independent study, if that is true the reflective nature of the product has less to do with it's performance than does the insulating properties.

Their product has a design that creates air pockets between the wall and the product, which acts as insulation. I wonder how much effect the reflective material, which is on the PVC product, plays in versus the insulating effect of the product.

Also, Novitherm states right up from on their home page that "If your building was built before 1980... your building is losing a significant amount of heat through the exterior walls." Why is it ineffective, or less effective on buildings build after 1980? My guess is that because those buildings have much more insulation in their walls. This would also support my theory that their product has much more to do with slowing the transfer of heat by insulation, and not as much by reflecting the radiated heat back to the room.

That being said. I believe radiators, both steam and hot water baseboard radiators produce radiation and convected heat, but that the ratio is something like 80% convective heat and 20% radiated heat (numbers found on the web, so I don't know really). I suppose the size and surface area may influence that ratio.

If there is a 10% percent energy savings, I'm surprised these types of products aren't sold in big box stores, or more talked about.

Various Techniques to Make Reflective Panels Found via Web Searching
1.
Cut cardboard to the size of your radiator, stick aluminum foil (some call it tinfoil) to it (shiny side out) and stick that with double-sided tape to the wall behind your radiator. This is green, cheap, and effective at reflecting back radiated heat, but I don't think it will do much as an insulator.

2. Do the same but instead of cardboard, stick the foil to a piece of foam board found at an art supply store. Perhaps there some insulating properties added with the foam board?

3. Buy a 1" think piece of rigid foam insulation that has foil facing (R-6.5), cut it to size and place that behind the radiator. Seems like a better idea than ideas one and two and doesn't cost much, and faster to make, but a bit too thick.

4. This was suggested by my energy auditor and is what I did. Buy some luaun board, cut to size, and stick foil-faced insulating bubble wrap to it. Details below.

A couple of things to note that I found in my web search
1.
In order for the radiator to do it job well, it must have proper clearance for the air to circulate through it to heat the air by convection on all sides. So whatever you do, it has been suggested that you must maintain at least 3/4 of an inch of open air space behind your radiator and the wall.

2. If you don't seal the perimeter of the reflector well, you could have a moisture/mold problem behind it. The reason is that if the wall behind is cold and the hot air coming off the radiator gets back there, the air might condense there, leaving moisture. I'll check mine periodically for this, as I didn't make an air-tight seal around my radiator reflectors.

3. Radiator Heat/Reflector Panels are typically only placed on radiators that are next to exterior walls and not interior walls. The thinking is that the heat lost to interior walls will be given off to the house interior anyway, so it's not lost. I suppose that's true, unless your interior wall is open and leads right up to an unfinished, unsealed wall header. Some even paint a dark color behind interior radiators to encourage the heat transfer as the wall will give off an even heat.

4. Hot water radiators get to 180 degrees, while steam radiators get to 212 degrees. So whatever you put behind there, be sure it can handle the heat safely. The reflective foil bubble wrap I used is rated to 160 degrees F., so I think they might melt if they were in contact. I made sure mine were well attached to the wall and definitely didn't make contact with the radiators. In fact if they do make contact, then you will transfer heat from the radiator to the reflective panel via "conduction" (the transfer of heat through solid matter), which would then conduct to your wall...

Here's How I Made Mine for my Big Steam Heat Radiators
I don't have the steps photographed but it's so simply, you'll get it.

(UPDATE 10/30/2009: Reflectix, Inc. now advertises it's foil faced bubble material, which is the stuff I used as a solution, to go behind hot water radiators, they say nothing about steam radiators. It can be purchased at HD. Here's a link to their short article on easy installation, using double-sided tape, Velcro, and so on to adhere the material. In their short introduction they don't actually say anything about energy savings, they just say, it will "increase the heat transmitted to the interior of a room..." "This will result in a more comfortable room at a lower thermostat setting.")


This is an after shot with the reflector installed behind the steam radiator. By the way, these radiators which originally would have been black, were painted by our previous home owner. They do look pretty, but the metallic paint hurts the radiant heating ability. All is not lost thought. That heat isn't wasted, it's still in the pipes, just takes longer to get it out to heat the rooms.


Here's another after shot. You can see I didn't go all the way down to the floor, as there was trim there, and I wanted the panel to lie flat against the wall. You can also see, barely, in the upper right corner of the reflector, a screw and washer combo. I have one of these in each corner.

Step by Step
1. Measure as big or slightly bigger than the radiator. I made my a bit shorter in height, as I wasn't sure how the wife would take the aesthetics of it all.

2. Measure and mark a piece of luaun (thin cheap wood found at HD) with a t-square, cut it with a jigsaw.

3. Measure, mark and cut a piece of insulated foil about an inch larger than you need it on all sides.

4. Add some glue to the Luaun in the middle and all around near the edges. I used some old roofing caulk I had around, as it said it was good for metal and rubber. I don't know if it will give off some toxic fumes, but so far I've not smelled anything and the panels are also always cool to the touch even when the radiators are heating.

5. Stick the reflective foil to the luaun. Smooth it out and flip it over. Cut off the overhanging foil with a utility knife.

6. Put the panel in place behind the radiator and drill some holes through the panel and into the wall for the correct size for the wall screw anchors you are going to use (use a long drill bit if the radiator is in the way). My drill bit kept wanting to wrap the reflective foil on to it while I drilled, as the glue wasn't dry yet between it and the wood. Just go slowly and watch for that, or let the glue dry first if you have that kind of patience.

7. Remove the panel, put in the screw anchors, and then replace the panel and screw in the screws with larger washers on them (so the don't go through the reflective foil). I used to long screw driver to get in around the radiators.

I made 8 of these and they all went on well. Now that they've been there for a month or two I do see some bowing out of the panels. So there is a small air space behind. I only anchored the 4 corners, perhaps more would be better.

Standing in front of the radiators I do not notice any difference at all. I also made so many other weatherization improvements in tandem, that I can't give you a good report on the results so far, as to energy savings. I can tell you that we barely see them and have now forgotten they are even there. So for cheap money, easy work, and something everyone can do, I say go for it. Whether it saves money, and when the pay off will kick in, I don't know, but I think in theory it seems to be a good thing to do.


Here's the reflective insulation / bubble wrap type stuff that I got at HD. It's made by Reflectix, Inc. It comes in big rolls and is about 3/8" thick. I'll add a link soon.


This photo shows the bubble layer better, which is the insulation. The material has a "variable R-value depending on the application", says the manufacturer. They say to see the various applications, listed on their site for R-values. I couldn't find any applications like this. But I didn't look that far. (UPDATE 10/30/2009: Reflectix's website now says for an application like this, the material is an R-3)


Here's the Luaun backing material I used. It's cheap, thin (3/8"), light and sturdy enough. Purchased at HD.


Here's everything you'll need if you make ones like mine. From left to rightish: tape measure (to measure size you want behind radiator); T-square (to make cut lines on the luaun and foil); Pencil (to mark the luaun and foil); Utility knife (to cut the insulated foil); glue (to adhere the luaun and reflective foil); Drill bits (to drill holes for the screw anchors, actually I didn't use the short ones shown in this photo. I used a super long drill bit, as the radiator was in the way); screws and screw anchors (to attach the panel to the wall); Washers (used with the screws so the screw ends don't go through the foil); Super long screw driver (used to tighten the screws that were had to get to as the radiator was in the way; Jigsaw (to cut the luan); Cordless Drill (to drill holes for the screw anchors)

Thanks to Paul Button at Energy Audits Unlimited for Suggesting this Project
Energy Audits Unlimited (Manchester, New Hampshire)
- Highly recommended

Materials
Reflectix: Reflective Insulation (Reflective/Bubble)
Luaun Board (They have it at HD)
Glue
Screws
Srcrew anchors
Washers

Resources
U.S. Department of Energy: Energy Saving Tips
U.S. Department of Energy: Reflectors Behind Steam Radiators
Cornell Cooperative Extension: Radidator Heat Reflectors
Novitherm Heat Reflectors
Massachusetts Department of Energy - Oil Heat Maintenace
MyTechGuide.com: Getting the Most from Radiators

Prefab Products
Novitherm Heat Reflectors
AM Conservation Group - Radiator Reflectors

Other Home Energy Links
Colorado Energy: R-Value of Materials
DOE: Insulation Calculator by Zip Code
Healthy House Institute
HGTV Insulation Forum
Home Energy Articles to '99
DoItYouself Insulation Forum
U.S. Department of Energy

My Standard Disclaimer: This is what I did. This does not mean this is the best way, the right way, to building code, or even safe for your needs. So you are on your own with your project. I make no promises about the information presented here. I'm just a do-it-yourselfer, not a professional at all, sharing my story. So if something goes wrong with your project, you are on your own. Good luck, and have fun!

All content and photos, copyright 2009, Dover Projects.

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23 comments:

  1. Thank you so much for posting the information on the radiator reflector heat panels. I have spent so much time trying to find them. I had attempted to order them from UK sites, but each one did not deliver to the US. I found one (ShopEco) via the link that you provided. I did not feel confident enough to make them myself and wanted to get them pre-made. You have made my day. :)

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  2. Did I provide a link to ShopEco? I did a search on my page here, and in Google and could not find the link you are reffering to. Please let me know the full link and I'll post as a resource. Thank you--Peter

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  3. Your "other prefab products" link brings you to the ShopEco site.

    I have copied part of the following from the beginning of your blog; you state:

    "Here's what you'll find from a Google web search:
    1. The UK sells lots of radiator reflector foil and other prefab products"

    Thanks again.

    ReplyDelete
  4. I just clicked on your "other prefab products" links and it brought me to the ShopEco site so it still works.

    Here is the site:
    http://www.shopeco.co.uk/index.aspfunction=DISPLAYPRODUCT&productid=304

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  5. Ah, thanks for explaining. I was thrown off when you said the ones in the UK didn't deliver. So I was looking for a US based site. But I get now that you are saying they do deliver to the US. Thanks--Peter

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  6. I received the following email from ShopEco this morning:

    "We want to let you know that your order status has been updated to...

    REFUNDED - Order refunded on July 10th 2009 - Cannot ship to the United States. Apologies for any inconvenience caused."

    Errr!

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  7. Hi Peter
    Nice article, I hope your wife is pleased with the result! I'm just thinking of doing something similar for one of my radiators. A couple of years ago I had some Infra red thermal pictures taken of my house. The walls are 14 inches thick made of air bricks and externally rendered but not insulated. You can very clearly see which radiator is losing heat to the outside wall even though it isn't set back into a niche like the others which do have insulating material behind them. The insulating material is not reflective, I guess it just traps air, and it's painted over, but seems (from the photos) to work. Thought you might be interested.
    Regards
    Dean

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  8. Dean,

    My wife is please with them. Meaning she doesn't even see them anymore and either do I. We left them up all summer and nobody has ever commented on them.

    I also had thermal pictures done, but only after I installed the reflectors. I don't have before shots unfortunately. If you get after shots, please share. Anyway, in the after shots the radiators didn't show up in the thermal photos at all. So they seem to be working, but again, without before shots, it's unscientific. Thanks for your comments.--Peter

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  9. Great article, very informative! Thanks man!

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  10. Just to amplify on your analysis of radiator reflectors:
    (a) reflectors made from kitchen foil will soon become inefficient, as aluminium oxidates very quickly and then loses its reflective quality.
    (b)There are only two radiator reflectors approved for use in the UK Government's Carbon Emission Reduction target (CERT) Scheme administered by Ofgem (the UK's Regulator of energy companies) – Radflek and Heatkeeper (another name for the Novitherm product). Independent testing of Radflek for the CERT Scheme has shown that Radflek is 23% more efficient than Heatkeeper/Novitherm. All third party test data for Radflek is disclosed on its website (http://www.radflek.com) unlike its competitors.

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  11. Michael, thanks for your comments and link!--Peter

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  12. NEW!!! DOVER PROJECTS ON FACEBOOK! Join in with your DIY spirit! Click on the BIG blue box for "Facebook, Dover Projects" in the right column above! See you there!--Peter

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  13. Why not use the same insulation material you show being applied to rim joists, with reflective side facing out for the radiators. It comes in 1", adds R value.

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  14. Anonymous: The rigid 1" foam board would be too think to put behind my radiators, thus hurting the flow of air around the radiator (convention performance). But if you had the space, might be a good idea. The rigid board is not as reflective to my eye though, so might not be as good at radiating....

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  15. Thanks for the DIY tips. Been looking into this for a little while now.

    FYI: Anyone still looking for prefab material can find it at the amconservationgroup.com site:
    http://www.amconservationgroup.com/store/pc/viewCategories.asp?idCategory=477

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  16. Hello,

    Another supplier for the bubble/foil insulation needed to make these is http://www.EcoFoil.com. We sell products which are Foil/Bubble/Foil and just Bubble/Foil. Having two layers of foil (we also sell with double bubble) and extra bubble insulation will definately help insulation; however, those working on a budget will find significant cost savings in just using the single bubble/foil solution.

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  17. Sure thing. Go ahead and steal photos if you like, just use credits with a link back if possible. Thanks!—Peter

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  18. Greetings Peter!

    What amazing info you have. You commented that the silver paint reduces heat output. Can you site your sources for that info? Or explain what would be better? We're planning to have our steam radiators sandblasted and the sandblaster recommends painting them in order to prevent rusting.

    Thanks,
    Rachel

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  19. Anonymous. This site: www.heatinghelp.com is an excellent resource for all sorts of heating questions, particularly steam heat. Here's a link to an article that should help you in the color of your radiators. It's not an easy answer you will see. http://www.heatinghelp.com/article/158/Radiators/1265/Does-the-Color-of-a-Radiator-Matter On that site there is also an "Ask a Question" section. There are true experts there that will answer any other questions you might have. Thanks for asking about the source.--Peter

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  20. Quick question. Have you tried extending the reflective material above the radiator and have it extend out from the wall over the radiator? I would think this would help force the hot air produced by the radiator into the center of the room instead of straight up. I just bought an old house and I think thats what I'm going to try in a couple of my colder rooms. Any thoughts?

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  21. Very thorough ;) I did the same, but just cut the reflectix to size and dropped it behind the radiator. :) It's been fine for several years now but not as pretty as yours!

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  22. Peter,

    I live in New York and have recessed radiators (steam system). I and am thinking of purchasing the Novitherm heat reflector product. I'm not sold on the effectiveness of the foil products out there such as EcoFoil and AMconservationgroup.com. What are your thoughts on the PVC heat reflector offered by Novitherm? They mention that an independent study by the University of Waterloo showed the Novitherm product reflects 94% of radiant heat.

    Thanks.

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Please leave your questions or comments here. I love to get feedback. You can do so without an account or user names and passwords, etc. Just select "Anonymous" next to "comment as". Thanks!--Peter