Roof heating. Choosing the best option for the anti-icing system

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“Prepare the sleigh in the summer, and the cart in the winter,” says popular wisdom. That is why summer is the ideal time of the year to prepare for the winter fight against the ice that forms on the roof of your own home. This article will show you how to do it without overpaying..

Roof de-icing

Icing of the roof often leads to leakage, destruction of the drainage system, or even just household injuries (a piece of ice that fell off the roof can kill). It is too late to complain about careless builders or weather conditions in such cases. There is a problem and it must be solved. The easiest and most obvious way is to remove snow and ice mechanically, simply by cleaning it off your roof. Unfortunately, the simplest option is rarely the best. Climbing a winter roof with a scraper and an ice ax, at least a couple of times a week, is not a pleasant pleasure. Not only is it hard physical labor, but the roof itself with such a frequent visit is quite real to damage. So if this is not the roof of some industrial or administrative building with a convenient exit to it and an employee specially hired for such tasks, but the roof of your own house, then this option of mechanical cleaning disappears by itself. What remains?

The second way out of the situation is suggested by logic itself. If the ice cannot be cleaned off, then it can simply be melted, or even better not to let it form. Before delving into the essence of this issue, let’s figure it out, where, in fact, does this ice come from? As you know, snow does not turn into an ice massif. In order to make ice, the snow cover must melt and only then freeze..

It goes like this. Warm air in the room tends upward (since it is lighter than cold air) and heats the roof, while it heats unevenly. Above the ridge, the roof warms up more (again, warm air tends upward), and closer to the cornice it is less. The cornice itself blown from all sides will remain completely cold..

Roof de-icing

What happens: the snow, protected from frost by its own pillow, begins to melt from the heated roof. Water under its mass rushes down the slope, cools down in cold areas, partially transforming into an ice crust on the cornice, and partially falling into the cold drain gutter of the drainage system, and freezes there. The entire water drainage system gradually freezes, which leads to its inoperability. Now part of the melt water, jumping over the side of the groove, rushes to the ground, forming icicles, and part remains on the roof. Having received an emphasis in the form of the formed ice, the water rises to the places where the roofing materials overlap, freezes there, while increasing in volume and destroying the roof itself. The destruction of the drainage system is also possible. This is primarily due to the fact that, having received an unplanned ice load, the system deforms under its weight, or simply collapses.

Option one. Heating of a roof and drainage system with a self-regulating cable

Based on the above information, it follows that it is enough to heat the ice-forming sections of the roof, as well as the drainage system, and the problem is solved. This is exactly what firms specializing in solving such problems do. The only trouble is that, being at the same time dealers of companies producing heating equipment, such offices, in a natural desire to earn money, offer their customers not always the cheapest solutions. So, you will most likely be asked to heat the perimeter of your “hot” roof, as well as a drain gutter and a drain pipe. And all this with a modern self-regulating cable (for example, Nexans DP 40). At the same time, supply a couple of not the cheapest sensors for automation. For convenience, we will consider a simple gable roof of a one-story house with dimensions of 10 × 10 m, the slope angle will be 45 °, and we will take the cold section 60 cm.First, we will calculate the approximate volume of the cable itself. For such a roof, this will be 2.2 m for each running meter of the slope. Total: (10 + 10) x 2.2 = 44 m.

Roof de-icing

A gutter for such a roof will be quite enough and 15 cm wide, which means that only one cable is needed to heat it. Let’s say the height to the cornice is 3 m, and the depth of soil freezing is 1.5 m, then we have: (10 + 3 + 1.5) x 2 = 29 m.

Add a meter to the inlet plus a meter to each drain pipe and get: 1 + 2 + 29 + 44 = 76 m. We multiply this figure by the average price of a product, which is 750 rubles: 76 x 500 = 57,000 rubles.

Fittings, sensors and a control cabinet will cost about 10,000 rubles, a total of 67,000 rubles. Add here at least 30% of the amount received, which the installers will take for their services, you get a very decent amount of 87,100 rubles. For ten years, we will spend about 5% of the cost of the system on repair work. This will amount to 4355 rubles.

Roof de-icing

But this is not all our waste. Average power consumption of a cable is 30 W / m. 76 x 30 = 2.28 kW per hour, that is 2.28 x 24 = 54.7 kW per day. Manufacturers say that in central Russia such a system will work for a maximum of 47 days per season, that is 54.7 x 47 = 2570 kW.

Let’s multiply this amount by 2.90 rubles. and we learn that now every year we will pay an additional 7455 rubles. for electricity. In 11–12 years these costs will be equal to the cost of the system itself. The total cost of the system and its operation for 10 years will be 166005 rubles.

Option two. Heating of the roof and drainage system with a constant power cable

And now let’s see what happens if we use a constant power cable instead of a self-regulating one. To do this, we need two pieces of cable 44 m each and two pieces of 29 m each.The power of the cable should be about 20 W.

Important: A huge disadvantage of such heating elements is their constant length specified by the manufacturer. Damage to such a cable in only one section leads to the failure of the entire element as a whole..

For heating the roof, we will take Deviflex DTIP-18, there are pieces of 44 m in the assortment, which is more than satisfactory for us. The power of one such element is 792 W, and the cost is 6978 rubles.

For heating trays and drainage systems, the same Deviflex DTIP-18 with a segment of 29 m is suitable.It should be said that usually it is rarely possible to select segments clearly in size and you have to overpay and take with a margin. The cost of the cable will be 5292 rubles, and its power is 522 W.

Roof de-icing

In total, we will spend only 24,540 rubles for the cable. instead of 57,000 rubles calculated for the purchase of a self-regulating cable.

We will not go anywhere from buying sensors, accessories and a thermostat, so we add another 10,000 rubles to the amount received. We get 34540 rubles. + 30% for installation = RUB 44,902, instead of RUB 87,100 when using a self-regulating cable.

Now let’s look at the operation. Such a system will consume 2.63 kW per hour.. (792 + 522) x 2 = 2628 W. For a day it is: 2.63 x 24 = 63.12 kW, if we multiply by 47 days of continuous operation per year, we get 2967 kW. At a cost per kW 2.90 rubles. this will amount to 8604 rubles. in year. For ten years, this amount will be 86,040 rubles.

Roof de-icing

But that’s not all waste. The fact is that the constant power cable is rather finicky in operation. It is necessary to constantly and carefully monitor the cleanliness of the roof and trays, so as not to get a place of local overheating. And still breakdowns will happen sooner or later. But only in the case of those, it will be necessary to change the entire length of the cable as a whole. Over 10 years, the amount spent on repairs can be up to 30% of the cost of the system. And this is 13 470 rubles.

In total, a ten-year operation of such a system will cost its owner 144,412 rubles, which is 21,593 rubles. less than making and operating a smart cable system. In return, the “thrifty” developer gets a headache in the form of keeping the system perfectly clean. Considering that a resistive cable consumes more electricity and is more expensive to repair, then every year the operation of a “smart” cable will be more profitable, and additional work on the maintenance of the constant power cable will not go anywhere.

As you can see, the second option also involves significant financial waste..

Option three. Cold roof fabrication and heating of the drainage system

To find other options, you need to look at the heart of the problem. Why does the snow melt on the roof? The main reason is the heating of the roof itself by the warmth of the room. And if the roof is insulated and the attic is ventilated? Maybe it will be cheaper than heating the street of your hometown? Let’s count.

Material, work per m2 price, rub.
Thermal insulation Ursa M-11 (15 cm) 340
Wooden bar 25×50 (6 cm) 50
Expendable materials 15
Installation cost 150
Suma 555

Two slopes 7×10 is 140 m2 roofs. In order to insulate one meter, you need 550 rubles. A total of 140 m will require 77,700 rubles. The perimeter of such a roof, as a rule, does not need to be heated. The snow melts on it only from solar heating, and it warms up the roof evenly. So you only need to heat the gutter and gutters, where we will lay the Freezstop-S30 self-regulating cable at the price of 596 rubles. And that’s all 29 x 596 = 17248 rubles.

Roof de-icing

The price of fittings will decrease slightly, so instead of 10,000 rubles. (sensors, weather station, fittings, power cables, etc.) we will keep within 8000 rubles. Such a system also has the likelihood of breaking, we will lay the same 5% for this, that is, over 10 years of operation, we will add another 1262 rubles. Another 7574 rubles. will have to be paid to installers (30% of the cost of materials).

Now about power consumption. 29 m of cable will consume 0.87 kW per hour, that is, 20.88 kW per day. But for a cold roof, the number of “working” days will decrease by at least a third, that is, not 47 days, but only 30: 30 x 20.88 = 626.4 kW. We multiply by the price of electricity: 626.4 x 2.9 = 1817 rubles. Over ten years, this amount will grow to 18,170 rubles. The cost of manufacturing and operating such a system for 10 years will be 140,132 rubles.

Roof de-icing

It can be seen from the calculations that the most promising option is the manufacture of a cold roof and heating of gutters and drain pipes. Such a roof will not only consume less electricity, it will also save a lot of energy resources spent on heating the room..

These calculations are approximate and do not claim to be absolutely accurate. They are presented in order to show the developer the differences between the various roof de-icing options. The optimal solution to the problem can be offered only after an accurate engineering calculation made by an independent specialist, but not by a dealer company..

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