Baseboard Heat Shield / Chimney

In our apartment the only place for our TV (and all associated electronics) is directly in front of one of the electric baseboard heaters in our living room. I didn't think much of this when we moved in, and ended up placing the solid TV stand directly up against the baseboard. To the right of the TV stand I build a lower stand to support our large laser printer. I build this stand so that the back of the printer would actually overhand the baseboard. The back of the printer was only around an inch above the baseboard. The printer stand was created with a slot in it below the printer. Last winter there was nothing in this slot, which was a good thing as I often noticed that the air temperature in the slot was very high. Since the baseboard hot air exhaust is directly behind the slot, the high temperature here was to be expected. Sometime this Spring I pulled the printer forward and realized that a small plastic cover at the bottom rear of the printer was alarmingly melted. At this point I finally realized what I had done in placing the TV and printer stand directly in front of the baseboard. However, since it wasn't practical to move all of these electronics to another location, I realized that I would need to build a heat management system for the baseboard.

My initial thought was to build a shroud with small fans to pull hot air away from the baseboard. However, such a system could easily overheat if the fans were to fail. Instead, I decided to take advantage of natural convection by constructing a "chimney" on top of the baseboard. Baseboard heaters are designed such that cool air enters them at the bottom. The air is heated across the heating elements before being exhausted at the top. Since hot air is less dense than cool air, it rises (think hot air balloon). The hot air rising out of the top of the radiator creates a small vacuum behind it, which "pulls" the cool air into the bottom of the radiator. This process of hot air rising is known as natural convection. Since the hot air leaving the baseboard will continue to rise, if a chimney is constructed on top of the baseboard, the air will naturally rise up the chimney. Instead of directly being exhausted onto the TV stand or printer, the hot air would be sent upward and into the room.

I used a second baseboard in the room (it was not hidden behind the TV) to create a Sketchup model of the baseboard, which the chimney was designed to fit. Since the baseboard exhausted hot air out of an angled slot at the top, the designed chimney (heat shield) could be placed directly on top of the baseboard, allowing the TV stand and printer to remain in place directly up against the baseboard. I designed the chimney to be 13" wide due to the limitations of my sheet metal brake. 5 of these chimneys would need to be constructed and placed side by side to cover the entire baseboard.

I made the heat shield from 14" wide aluminum flashing. Two 10' rolls were sufficient for creating the 5 shields. The flashing was easily cut using tin snips (aviation snips), and rivets were used to secure the pieces together. I used 1/8" diameter aluminum rivets.

I created one heat shield and test fit it over the radiator behind the printer. Almost immediately I realized I had made a serious mistake. The radiator behind the TV was significantly different from the second radiator in the room, which was the one I had based my design on. The difference was that the actual radiator exhausted the hot air horizontally instead of at an angle. Because of this difference, a small gap was added to the shield in front of the radiator. This gap would require the TV and printer be moved forward by around 3/4". After updating the shield design, I set to work building it.

Each shield was constructed from two pieces of flashing; a front and back piece. These two pieces are riveted together to form the complete shield. The back piece is prepared by cutting a 9" x 19.5" rectangle of flashing. Angled cuts are made in each end of this rectangle, to the dimensions shown in the picture above. A bend line was also drawn at a distance of 3.25" from each of the ends.

My sheet metal brake was used to bend the back along the prepared bend lines. The ends of the back were bent to 90°. These ends would form the sides of the completed shield.

The front is prepared from a 14" x 15" rectangle of flashing. Bend lines were drawn across this rectangle at a distance of 4.5" from the bottom and 7.25" from the top. The total top to bottom dimension is 14", with 15" being the dimension across the front. Small 3/8" wide strips were cut along each side between the bottom and the 4.5" bend line. Next, bend lines were drawn along the sides of the front; 1" in from each side. This 1" strip will be bent to 90° and will form tabs for riveting to the back. This 1" strip was cut at the 4.5" and 7.25" bend lines to allow for the tabs to be bent after the long bends across the front are made.

I found that it was easiest to drill the rivet holes in the front piece before bending. Since we were using 1/8" rivets, the next bit size larger than 1/8" was used for these holes. The holes were placed near the ends of the 1" wide side tabs.

Once the front piece was cut and rivet holes were drilled in it, the long bends were made (the 4.5" and 7.25" bend lines) using the brake. These angles were not made to 90°. I just eyeballed these angles and if they were bent too far I found that I could relax the angle slightly by running my finger along the backside of the bend, while it was facedown on the table.

The 1" wide tabs on the sides of the front were bent to 90° using a Vise Grip sheet metal tool. For the bends wider than the width of the tool, I would bend a portion of it to an angle less than 90° and then bend the next portion of the bend to the same angle. Once the entire tab was partially bent, I came back and repeated the process until I reached the final 90° angle.

The back and front parts were fit together with the front tabs overlaying the sides formed by the bent edges of the back. A sharpie was used to mark the position of the holes on the sides of the back. Holes were drilled on these marks to the same size as the holes in the tabs.

After drilling the holes in the sides of the back piece, the shield was completed by riveting the front and back together.

After my mistake with the first shield, I made sure to test fit this shield before I constructed 4 more to cover the entire length of baseboard. This time the shield fit perfectly, so I proceeded to make 3 more identical shields and 1 with a few modifications.

Above the right end of the baseboard is an outlet, which is used to power almost everything along the wall. The shield next to this outlet needed to be modified to allow the outlet to remain functional, while still providing complete shielding of the baseboard. It was determined that the upper portion of the right side of the shield needed to be moved 2" to the left. The left side of the shield is identical to the 4 other shields. For the right side of the shield, the front piece was cut at an angle between the 4.5" and 7.25" bend line (see picture). The back piece is similar to the other shields except that it is 2" narrower (11" wide at the top").

A third piece was cut to form the small angled portion below the outlet. This piece measured 3 1/4" x 3 7/8" and was bent along lines 1" and 3/8" from the long edges. Two adjacent corners were cut out of both of these bent edges. The 1" wide edge between these cutouts was then bent to 90°. Finally, this third piece was completed by cutting away a portion of it at an angle. After drilling appropriate holes, the third piece was riveted to the front and back pieces - completing the right-most shield.

Once all 5 shields were completed, the TV and printer stands were pulled forward and the shields were fitted over the baseboard. As seen, all of the shields fit very well and the cutout in the right shield allows for access to the outlet. After the complete shield was in place, the TV and printer stands were pushed back against them.

This project can be considered a success if it allows for all of the electronics and furniture in front of the baseboard to remain cool. To test this I turned up the heat to 75° and let everything warm up for 15 minutes. After 15 minutes, I measured the temperature inside the top opening of the shield. This should be the hottest point of the shield. I measured temperatures of around 105°F, which is quite warm, but not dangerously hot. The other temperature I was concerned about was the shield temperature directly in front of the baseboard. If this temperature were too high it would heat up the slot beneath the printer as well as the rear surface of the TV stand. Surprisingly, I only measured a temperature of around 76°F here. I will continue to check on this system as the weather gets colder and the heater runs more, but at this point I feel confident that I have created a system, which safely allows for minimal clearance between the hot baseboard and furniture.