Resistance to heat transfer of entrance metal doors. Data on heat transfer resistance of windows, balcony doors and skylights of various designs
1.4 Heat transfer resistance of exterior doors and gates
For external doors, the required heat transfer resistance R o tr must be at least 0.6R ref of the walls of buildings and structures, determined by formulas (1) and (2).
0.6R about tr \u003d 0.6 * 0.57 \u003d 0.3 m² ºС / W.
Based on the accepted designs of external and internal doors, according to Table A.12, their thermal resistances are accepted.
External wooden doors and double gates 0.43 m² ºС/W.
Internal doors single 0.34 m² ºС/W
1.5 Heat transfer resistance of skylight fillings
For the selected type of glazing according to Appendix A, the value of thermal resistance to heat transfer of light openings is determined.
At the same time, the heat transfer resistance of the fillings of external light openings R ok must be not less than the standard heat transfer resistance
determined according to table 5.1, and not less than the required resistance
R= 0.39, determined according to table 5.6
Heat transfer resistance of the fillings of the light openings, based on the difference between the calculated temperatures of the internal t in (table A.3) and the outside air t n and using table A.10 (t n is the temperature of the coldest five-day period).
Rt \u003d t in - (- t n) \u003d 18- (-29) \u003d 47 m² ºС / W
R ok \u003d 0.55 -
for triple glazing in wooden split-pair bindings.
With a ratio of the glazing area to the area of filling the light opening in wooden bindings, equal to 0.6 - 0.74, the specified value of R ok should be increased by 10%
R \u003d 0.55 ∙ 1.1 \u003d 0.605 m 2 Cº / W.
1.6 Heat transfer resistance of interior walls and partitions
| Calculation of thermal resistance of internal walls | ||||
| Coef. thermal conductivity material λ, W/m² ºС | Note | |||
| 1 | Beam pine | 0,16 | 0,18 | p=500 kg/m³ |
| 2 | Name of indicator | Meaning | ||
| 3 | 18 | |||
| 4 | 23 | |||
| 5 | 0,89 | |||
| 6 | Rt = 1/αv + Rk + 1/αn | 0,99 | ||
| Calculation of thermal resistance of internal partitions | ||||
| Construction layer name | Coef. thermal conductivity material λ, W/m² ºС | Note | ||
| 1 | Beam pine | 0,1 | 0,18 | p=500 kg/m³ |
| 2 | Name of indicator | Meaning | ||
| 3 | coefficient heat transfer inside surface of the enclosing structure αv, W/m² ºС | 18 | ||
| 4 | coefficient heat transfer to the outside surfaces for winter conditions αн, W/m² ºС | 23 | ||
| 5 | thermal resistance of the enclosing structure Rк, m² ºС/W | 0,56 | ||
| 6 | heat transfer resistance of the enclosing structure Rt, m² ºС/W Rt = 1/αv + Rk + 1/αn | 0,65 | ||
Section 13. - tee per passage 1 pc. z = 1.2; - outlet 2 pcs. z = 0.8; Section 14. - outlet 1 pc. z = 0.8; - valve 1 pc. z = 4.5; The coefficients of local resistances of the remaining sections of the heating system of a residential building and a garage are determined similarly. 1.4.4. General provisions for the design of a garage heating system. System...
Thermal protection of buildings. SNiP 3.05.01-85* Internal sanitary systems. GOST 30494-96 Residential and public buildings. Room microclimate parameters. GOST 21.205-93 SPDS. Symbols of elements of sanitary systems. 2. Determination of the thermal power of the heating system The enclosing structures of the building are represented by external walls, a ceiling above the top floor ...
... ; m3; W/m3 ∙ °С. The condition must be met. The standard value is taken according to table 4, depending on. The value of the normalized specific thermal characteristic for a civil building (tourist base) . Since 0.16< 0,35, следовательно, условие выполняется. 3 РАСЧЕТ ПОВЕРХНОСТИ НАГРЕВАТЕЛЬНЫХ ПРИБОРОВ Для поддержания в помещении требуемой температуры необходимо, ...
Designer. Internal sanitary - technical devices: at 3 o'clock - H 1 Heating; ed. I. G. Staroverov, Yu. I. Schiller. - M: Stoyizdat, 1990 - 344 p. 8. Lavrent'eva V. M., Bocharnikova O. V. Heating and ventilation of a residential building: MU. - Novosibirsk: NGASU, 2005. - 40 p. 9. Eremkin A. I., Koroleva T. I. Thermal regime of buildings: Textbook. - M.: DIA Publishing House, 2000. - 369 p. ...
The difference between the outer entrance door to the house (to a cottage, office, shop, production building) and the inner entrance door to the apartment (office) is in operating conditions.
External entrance doors to the building are a barrier between the street and the interior of the house. Such doors are affected by sunlight, rain, snow and other precipitation, temperature and humidity changes.
External doors installed at the entrance to the building (at the exit to the street). These can be both access doors at the entrance to an apartment building, and doors to a private single-family house or cottage; external doors can also be part of the entrance group to an office building, a store or an industrial or administrative building. Despite the fact that all these external doors have different requirements, all external entrance doors, along with strength, must have increased weather resistance (to resist dampness, solar radiation, temperature changes).
Wooden exterior doors
Wood is the traditional material used to make doors. Solid wood exterior doors are used for installation in cottages and private houses. Wooden external doors in accordance with GOST 24698 installed in apartment buildings and public buildings. Exterior wooden doors are made single- and double-sided, with glazed and solid panel or frame panels. All wooden exterior doors have increased moisture resistance.
Possessing low thermal conductivity (the coefficient of thermal conductivity of wood λ = 0.15—0.25 W/m×K, depending on the type and humidity), wooden doors provide a high reduced resistance to heat transfer. The wooden front door in winter does not freeze, it is not covered with frost from the inside and the locks do not freeze in it (unlike some metal doors). Since metal is a good conductor, it quickly conducts cold from the street into the house, which leads to the formation of frost on the inside of the door and frame and the freezing of locks.
External entrance wooden doors type DN according to GOST 24698 installed in standard doorways in the outer walls of buildings.
Dimensions of standard doorways:
- opening width - 910, 1010, 1310, 1510, 1550 1910 or 1950 mm
- opening height - 2070 or 2370 mm
Plastic front doors
Plastic (metal-plastic) external entrance doors are made, as a rule, glazed from polyvinyl chloride profiles (PVC profile) for door blocks according to GOST 30673-99. As glazing, one- or two-chamber glued double-glazed windows according to GOST 24866 with a heat transfer resistance of at least 0.32 m² × ° C / W.
Plastic (metal-plastic) exterior doors combine an affordable price and high performance. Possessing low thermal conductivity (0.2-0.3 W / m × K, depending on the brand), polyvinyl chloride (PVC) makes it possible to produce warm plastic doors (according to GOST 30674-99) with a heat transfer resistance of at least 0.35 m²×°C/W (for a single-chamber double-glazed window) and at least 0.49 m²×°C/W (for a double-glazed window), while the reduced heat transfer resistance of the opaque part of the filling of plastic door blocks sandwiches not lower than 0.8 m² × ° C / W.
In a room that is not equipped with a cold vestibule, to eliminate condensation, frost and ice, a door with high heat-insulating properties should be installed. Wooden and plastic doors have the highest thermal insulation performance, so metal-plastic doors are an ideal option for an external entrance door to a single-family residential building or office.
Metal front doors
In the production of metal doors, either extruded profiles from aluminum alloys (aluminum doors) or steel hot-rolled and cold-rolled sheets and bars in combination with bent steel profiles (steel doors) are used.
By definition, a metal exterior door will be cold, since both steel, and even more so aluminum alloys, are excellent conductors of heat (low-carbon steel has a coefficient of thermal conductivity λ about 45 W / m × K, aluminum alloys - about 200 W / m × K, that is, steel is about 60 times worse in terms of thermal insulation than wood or plastic, and aluminum alloys are about 3 orders of magnitude worse.).
And on a cold surface, by definition, moisture will condense if the air in contact with it has excess moisture for a given temperature (if the temperature of the inner surface of the front door drops below the dew point of the indoor air). The use of decorative panels on a metal door without a thermal break will prevent freezing (hoarfrost), but not the formation of condensate.
The solution to the problem of freezing of metal exterior doors is the use of “warm” profiles with thermal inserts in the production of exterior entrance doors (the use of thermal breaks from materials with low thermal conductivity) or a device, that is, the installation of another door (tambour) that cuts off the warm and humid air of the main interior from the front door. For external metal doors (facing the street), the equipment of a thermal vestibule is a prerequisite ( clause 1.28 of SNiP 2.08.01"Residential Buildings").
Aluminum entry exterior doors
Aluminum external entrance doors GOST 23747 are made, as a rule, glazed using extruded profiles according to GOST 22233 from aluminum alloys of the aluminum-magnesium-silicon system (Al-Mg-Si) grades 6060 (6063). As glazing, one- or two-chamber glued double-glazed windows are used in accordance with GOST 24866-99 with a heat transfer resistance of at least 0.32 m² × ° C / W.
Aluminum alloys do not contain heavy metal impurities, do not emit harmful substances under the influence of ultraviolet rays and remain operational in any climatic conditions at temperature differences from − 80°С to + 100°С. The durability of aluminum structures is over 80 years (minimum service life).
Aluminum alloys grades 6060 (6063) are characterized by a fairly high strength:
- design resistance to tension, compression and bending R= 100 MPa (1000 kgf/cm²)
- temporary resistance σ in= 157 MPa (16 kgf/mm²)
- yield point σ t= 118 MPa (12 kgf/mm²)
Aluminum alloys better than any other material used in the manufacture of doors, retains its structural properties under temperature changes. After appropriate surface treatment of aluminum products, they become resistant to corrosion caused by rain, snow, heat and smog of large cities.
Despite the fact that aluminum alloys used in the manufacture of extruded profiles of the frame and leaf of external doors have a very high coefficient of thermal conductivity λ about 200 W / m × K, which is 3 orders of magnitude higher than that of wood and plastic, due to constructive measures using thermal breaks from materials with low thermal conductivity, it is possible to significantly increase the heat transfer resistance in “warm” aluminum profiles with thermal inserts up to 0, 55 m²×°C/W.
Swing aluminum exterior doors are most often installed in shopping and business centers, shops, banks and other buildings with high traffic, where the main requirement is high reliability of the door structure. In the manufacture of external entrance doors, as a rule, “warm” profiles with thermal breaks are used. But quite often in practice, in order to save money, in vestibule systems, in the presence of a thermal curtain, "cold" aluminum profiles are also used.
Steel entrance exterior doors
Steel external entrance doors in accordance with GOST 31173 have the greatest strength. They are usually made deaf.
Perm production company "GRAN-Stroy" carries out production to order and installation of external steel metal entrance doors in accordance with GOST 31173. The cost of ordered external steel doors depends on their configuration and finish class. The minimum price of a steel outer door is 8500 rubles.
The leaf of the outer entrance door is made of hot-rolled steel sheet in accordance with GOST 19903 with a thickness of 2 to 3 mm on a frame of a steel rectangular pipe with a cross section of 40 × 20 mm to 50 × 25 mm. The inside is finished with tinted smooth or milled plywood with a thickness of 4 to 12 mm. Door leaf thickness up to 65 mm. Between the steel sheet and the plywood sheet there is a heater, which also performs the function of noise insulation. Doors are equipped with one or two mortise three- or five-bolt locks with lever and (or) cylinder mechanisms of the 3rd or 4th class according to GOST 5089. Two sealing circuits are installed in the porch.
The main regulatory requirements for entrance doors are set out in the following sets of building codes and regulations (SP and SNiP):
- SP 1.13130.2009 “Fire protection systems. Evacuation routes and exits ";
- SP 50.13330.2012 "Thermal protection of buildings" (updated version of SNiP 23-02-2003);
- SP 54.13330.2011 "Residential buildings multi-apartment" (updated edition
According to table A11, we determine the thermal resistance of external and internal doors: R nd \u003d 0.21 (m 2 0 C) / W, therefore, we accept double outer doors; R vd1 \u003d 0.34 (m 2 0 C) / W, R vd2 \u003d 0.27 (m 2 0 C) / W.
Then, using formula (6), we determine the heat transfer coefficient of external and internal doors:
W / m 2 about C
W / m 2 about C
2 Calculation of heat losses
Heat losses are conditionally divided into basic and additional.
Heat losses through the internal enclosing structures between the premises are calculated if the temperature difference on both sides is >3 0 С.
The main heat losses of the premises, W, are determined by the formula:
where F is the estimated area of \u200b\u200bthe fence, m 2.
Heat losses, according to formula (9), are rounded up to 10 W. The temperature t in the corner rooms is taken 2 0 C higher than the standard. We calculate heat losses for external walls (NS) and internal walls (VS), partitions (Pr), floors above the basement (PL), triple windows (TO), double external doors (DD), internal doors (DV), attic floors (PT ).
When calculating heat losses through the floors above the basement, the outside air temperature t n is taken to be the temperature of the coldest five-day period with a security of 0.92.
Additional heat losses include heat losses that depend on the orientation of the premises in relation to the cardinal points, on wind blowing, on the design of external doors, etc.
The addition to the orientation of the enclosing structures along the cardinal points is taken in the amount of 10% of the main heat losses if the fence is facing east (E), north (N), northeast (NE) and northwest (NW) and 5% - if west (W) and southeast (SE). The additive for heating the cold air rushing in through the outer doors at the height of the building H, m, we take 0.27N from the main heat losses of the outer wall.
Heat consumption for heating the supply ventilation air, W, is determined by the formula:
where L p - supply air consumption, m 3 / h, for living rooms we take 3 m 3 / h per 1 m 2 of living quarters and kitchen area;
n - the density of the outside air, equal to 1.43 kg / m 3;
c - specific heat capacity, equal to 1 kJ / (kg 0 С).
Household heat releases supplement the heat transfer of heating devices and are calculated by the formula:
,
(11)
where F p is the floor area of the heated room, m 2.
The total (total) heat loss of the building Q floor is defined as the sum of the heat loss of all rooms, including staircases.
Then we calculate the specific thermal characteristic of the building, W / (m 3 0 C), according to the formula:
,
(13)
where is a coefficient that takes into account the influence of local climatic conditions (for Belarus 
);
V zd - the volume of the building, taken according to the external measurement, m 3.
Room 101 - kitchen; t in \u003d 17 + 2 0 C.
We calculate the heat loss through the outer wall with a northwest orientation (C):
outer wall area F = 12.3 m 2;
temperature difference t= 41 0 C;
coefficient taking into account the position of the outer surface of the building envelope in relation to the outside air, n=1;
heat transfer coefficient, taking into account window openings k \u003d 1.5 W / (m 2 0 C).
The main heat losses of the premises, W, are determined by the formula (9):
Additional heat loss for orientation is 10% of Qbase and is equal to:
Tue
Heat consumption for heating the supply ventilation air, W, is determined by the formula (10):
Household heat emissions were determined by the formula (11):
Heat costs for heating the supply ventilation air Q veins and household heat emissions Q household remain the same.
For triple glazing: F=1.99 m 2 , t=44 0 С, n=1, heat transfer coefficient K=1.82W/m 2 0 С, it follows that the main heat loss of the window Q main = 175 W, and additional Q ext \u003d 15.9 W. The heat loss of the outer wall (B) Q main \u003d 474.4 W, and the additional Q ext \u003d 47.7 W. The heat loss of the floor is: Q pl. \u003d 149 W.
We sum up the obtained values of Q i and find the total heat loss for this room: Q \u003d 1710 W. Similarly, we find heat losses for other rooms. The results of the calculation are entered in table 2.1.
|
Table 2.1 - Sheet for calculating heat losses |
|||||||||||||||
|
room number and purpose |
Fencing surface |
temperature difference tv - tn |
Correction factor n |
Heat transfer coefficient k W/m C |
Main heat losses Qbase, W |
Additional heat loss, W |
Heat Sweat. on the filter Qven, W |
Genesis heat output Qlife, W |
General heat loss Qpot \u003d Qmain + Qadd + Qven-Qlife |
||||||
|
Designation |
Orientation |
The size a, m |
The size b, m |
Area, m2 |
Orientation | ||||||||||
Continuation of table 2.1
Continuation of table 2.1
Continuation of table 2.1
|
ΣQ FLOOR= 11960 |
|||||||||||||||
After the calculation, it is necessary to calculate the specific thermal characteristic of the building:
,
where α-coefficient, taking into account the influence of local climatic conditions (for Belarus - α≈1.06);
V zd - the volume of the building, taken according to the external measurement, m 3
The resulting specific thermal characteristic is compared by the formula:
,
where H is the height of the calculated building.
If the calculated value of the thermal characteristic deviates by more than 20% compared to the standard value, it is necessary to find out the reasons for this deviation.
,
As 
<
we assume that our calculations are correct.
Thermal insulation (thermal protection)
Thermal insulation is one of the main functions of the window, which provides comfortable conditions indoors.
The heat loss of a room is determined by two factors:
- transmission losses, which are made up of heat flows that the room gives off through walls, windows, doors, ceiling and floor.
- ventilation losses, which is understood as the amount of heat required to heat up to room temperature cold air penetrating through window leaks and as a result of ventilation.
In Russia, to assess the heat-shielding characteristics of structures, it is accepted heat transfer resistance R o(m² · °C/W), the reciprocal of the thermal conductivity k, which is accepted in DIN standards.
Thermal conductivity coefficient k characterizes the amount of heat in watts (W) that passes through 1m² of construction with a temperature difference on both sides of one degree on the Kelvin (K) scale, the unit of measure is W / m² K. The lower the value k, the less heat transfer through the structure, i.e. higher insulating properties.
Unfortunately, a simple recalculation k in R o(k=1/R o) is not quite correct due to the difference in measurement methods in Russia and other countries. However, if the product is certified, then the manufacturer is obliged to provide the customer with an indicator of resistance to heat transfer.
The main factors affecting the value of the reduced heat transfer resistance of the window are:
- window size (including the ratio of the glazing area to the area of the window block);
- cross section of the frame and sash;
- window block material;
- type of glazing (including the width of the distance frame of the double-glazed window, the presence of selective glass and special gas in the double-glazed window);
- number and location of seals in the frame/sash system.
From the value of indicators R o also depends on the surface temperature of the enclosing structure facing the inside of the room. With a large temperature difference, heat is radiated towards the cold surface.
Poor heat-shielding properties of windows inevitably lead to the appearance of cold radiation in the area of windows and the possibility of condensation on the windows themselves or in the area of their adjoining to other structures. Moreover, this can occur not only as a result of the low heat transfer resistance of the window structure, but also due to poor sealing of the frame and sash joints.
Heat transfer resistance of enclosing structures is standardized SNiP II-3-79*"Construction Heat Engineering", which is a reissue SNiP II-3-79"Construction Heat Engineering" with amendments approved and put into effect on July 1, 1989 by Decree of the USSR Gosstroy of December 12, 1985 241, Amendment 3, put into effect on September 1, 1995 by Decree of the Ministry of Construction of Russia of August 11, 1995 18-81 and change 4, approved by the Decree of the Gosstroy of Russia of January 19, 1998 18-8 and put into effect on March 1, 1998
In accordance with this document, when designing, the reduced heat transfer resistance of windows and balcony doors R o should take at least the required values, R o tr(see table 1).
Table 1. Reduced heat transfer resistance of windows and balcony doors
| Buildings and constructions | Degree-day of the heating period, °C day | Reduced resistance to heat transfer of windows and balcony doors, not less than R neg, m² · °C/W |
|---|---|---|
| Residential, medical and preventive and children's institutions, schools, boarding schools | 2000 4000 6000 8000 10000 12000 |
0,30 0,45 0,60 0,70 0,75 0,80 |
| Public, except for the above, administrative and domestic, with the exception of premises with a humid or wet regime | 2000 4000 6000 8000 10000 12000 |
0,30 0,40 0,50 0,60 0,70 0,80 |
| Production with dry and normal mode | 2000 4000 6000 8000 10000 12000 |
0,25 0,30 0,35 0,40 0,45 0,50 |
| Note: 1. Intermediate values R neg should be determined by interpolation 2. The norms of resistance to heat transfer of translucent enclosing structures for premises of industrial buildings with a humid or wet regime, with excess sensible heat from 23 W / m 3, as well as for premises of public, administrative and domestic buildings with a humid or wet regime should be taken as for premises with dry and normal conditions of industrial buildings. 3. The reduced heat transfer resistance of the blind part of balcony doors must be at least 1.5 times higher than the heat transfer resistance of the translucent part of these products. 4. In certain justified cases related to specific design solutions for filling window and other openings, it is allowed to use the design of windows, balcony doors and lanterns with a reduced heat transfer resistance of 5% lower than that specified in the table. |
||
Degree-days of the heating period(GSOP) should be determined by the formula:
GSOP \u003d (t in - t from.per.) · z from.per.
where
t in- design temperature of internal air, °C (according to GOST 12.1.005-88 and design standards for relevant buildings and structures);
t from.per.- average temperature of the period with average daily air temperature below or equal to 8°C; °C;
z from.trans.- duration of the period with an average daily air temperature below or equal to 8°C, Days (according to SNiP 2.01.01-82"Construction climatology and geophysics").
By SNiP 2.08.01-89* when calculating the enclosing structures of residential buildings, it should be taken: the temperature of the internal air is 18 ° C in areas with the temperature of the coldest five-day period (determined in accordance with SNiP 2.01.01-82) above -31 ° C and 20 ° C at -31 ° C and below; relative humidity equal to 55%.
Table 2. Outside air temperature(optional, see SNiP 2.01.01-82 in full)
| City | Outside air temperature, °С | ||||
|---|---|---|---|---|---|
| The coldest five-day period | Period with average daily air temperature ≤8°C |
||||
| 0,98 | 0,92 | Duration, days | Average temperature, °С | ||
|
Vladivostok |
|||||
|
Volgograd |
|||||
|
Krasnoyarsk |
|||||
|
Krasnodar |
|||||
|
Murmansk |
|||||
|
Novgorod |
|||||
|
Novosibirsk |
|||||
|
Orenburg |
|||||
|
Rostov-on-Don |
|||||
|
St. Petersburg |
|||||
|
Stavropol |
|||||
|
Khabarovsk |
|||||
|
Chelyabinsk |
|||||
To facilitate the work of designers in SNiP II-3-79*, the appendix also contains a reference table containing the reduced heat transfer resistances of windows, balcony doors and skylights for various designs. It is necessary to use these data if the values R not in the standards or specifications for the design. (see note to table 3)
Table 3. Reduced heat transfer resistance of windows, balcony doors and skylights(reference)
| Filling the light opening | Reduced resistance to heat transfer R o, m² °C / W | ||
|---|---|---|---|
| in wooden or PVC binding | in aluminum binding | ||
|
1. Double glazing in twin sashes |
|||
|
2. Double glazing in separate sashes |
0,34* |
||
|
3. Hollow glass blocks (with a joint width of 6 mm) size, mm: |
0.31 (without binding) |
||
|
4. Profiled box glass |
0.31 (without binding) |
||
|
5. Double plexiglass for skylights |
|||
|
6. Triple plexiglass skylight |
|||
|
7. Triple glazing in separate-paired bindings |
|||
| 8. Single-chamber double-glazed glass: Ordinary |
|||
| 9. Double glazing made of glass: Conventional (with 6 mm glass spacing) Conventional (with 12 mm glass spacing) With hard selective coating With soft selective coating |
|||
| 10. Ordinary glass and single-chamber double-glazed window in separate glass bindings: Ordinary With hard selective coating With soft selective coating With hard selective coating and filled with argon |
|||
| 11. Ordinary glass and double-glazed window in separate glass bindings: Ordinary With hard selective coating With soft selective coating With hard selective coating and filled with argon |
|||
| 12. Two single-chamber double-glazed windows | |||
|
13. Two single-chamber double-glazed windows in separate bindings |
|||
|
14. Four-layer glazing in two paired bindings |
|||
| * In steel bindings Notes:
|
|||
In addition to the all-Russian regulatory documents, there are also local ones in which certain requirements for a given region can be tightened.
For example, according to the Moscow city building codes MGSN 2.01-94"Energy supply in buildings. Standards for thermal protection, heat and water supply.", Reduced resistance to heat transfer (Ro) must be at least 0.55 m² °C/W for windows and balcony doors (0.48 m² °C/W is allowed in the case of double-glazed windows with heat-reflecting coatings).
The same document contains other clarifications. To improve the thermal protection of the fillings of light openings in the cold and transitional periods of the year without increasing the number of glazing layers, glass with a selective coating should be used, placing them on the warm side. All porches of window frames and balcony doors must contain sealing gaskets made of silicone materials or frost-resistant rubber.
Speaking about thermal insulation, it must be remembered that in summer windows should perform the opposite function to winter conditions: to protect the room from the penetration of solar heat into a cooler room.
It should also be taken into account that blinds, shutters, etc. act as temporary heat shields and significantly reduce heat transfer through windows.
Table 4. Heat transmission coefficients of sun protection devices
(SNiP II-3-79*, Appendix 8)
|
sun protection devices |
Heat transfer coefficient |
|---|---|
|
A. Outdoor
|
0,15 |
|
Note:
1. Heat transmission coefficients are given in fractions: up to the line - for sun protection devices with plates at an angle of 45 °, after the line - at an angle of 90 ° to the opening plane. 2. The heat transmission coefficients of inter-pane sun protection devices with a ventilated inter-pane space should be taken 2 times less. |
|
In one of the previous articles, we discussed composite doors and briefly touched upon blocks with a thermal break. Now we dedicate a separate publication to them, since these are quite interesting products, one might say - already a separate niche in door construction. Unfortunately, in this segment, not everything is clear, there are achievements, there is a farce. Now our task is to understand the features of the new technology, to understand where technological "goodies" end, and where marketing games begin.
To understand how thermally separated doors work, and which of them can be considered as such, you will have to delve into the details and even remember a little school physics.
If you are still undecided, check out our offers
- This is a natural process of striving for balance. It consists in the exchange / transfer of energy between bodies with different temperatures.
- Interestingly, hotter bodies give off energy to colder ones.
- Naturally, with such a return, warmer parts cool down.
- Substances and materials with different intensity transfer heat.
- The definition of the thermal conductivity coefficient (denoted as c) calculates how much heat will pass through a sample of a given size, at a given temperature, per second. That is, in applied matters, the area and thickness of the part, as well as the characteristics of the substance from which it is made, will be important. Some metrics to illustrate:
- aluminum - 202 (W/(m*K))
- steel - 47
- water - 0.6
- mineral wool - 0.35
- air - 0.26
Thermal conductivity in construction and for a metal door in particular
All building envelopes transfer heat. Therefore, in our latitudes, there is always heat loss in a dwelling, and heating is necessarily used to replenish them. Windows and doors installed in openings have a disproportionately thinner thickness than walls, which is why there is usually an order of magnitude more heat loss here than through walls. Plus, the increased thermal conductivity of metals.
What problems look like.
Naturally, the doors that are installed at the entrance to the building suffer the most. But not at all, but only if the temperature differs greatly from inside and outside. For example, the common entrance door is always completely cold in winter, there are no particular troubles with steel doors for an apartment, because it is warmer in the entrance than on the street. But the door blocks of cottages work at the temperature limit - they need special protection.
Obviously, in order to exclude or reduce heat transfer, it is necessary to artificially equalize the internal and "outboard" temperatures. In fact, a large air layer is created. Traditionally, there are three ways:
- Allow the door to freeze by installing the second door block from the inside. The heating air does not make its way to the front door, and there is no sharp temperature drop - no condensate.
- They make the door always warm, that is, they build a vestibule outside without heating. It equalizes the temperature on the outer surface of the door, and heating warms up its inner layers.
- Sometimes it helps to organize an air thermal curtain, electric heating of the canvas or underfloor heating near the front door.
Of course, the steel door itself should be insulated as much as possible. This applies to both the cavities of the box and the canvas, and the slopes. In addition to cavities, linings work to resist heat transfer (the thicker and "fluffier" - the better).
Thermal break technology
The eternal dream of the developer to forever and irrevocably defeat heat transfer. The disadvantage is that the warmest materials tend to be the most brittle and weakly supportive, due to the fact that heat transfer resistance is highly dependent on density. To strengthen porous materials (which contain gases), they must be combined with stronger layers - this is how sandwiches appear.
However, the door unit is a self-supporting spatial structure that cannot exist without a frame. And then other unpleasant moments appear, which are called "cold bridges". This means that no matter how well the steel front door is insulated, there are elements that pass through the door. These are: the walls of the box, the perimeter of the canvas, stiffeners, locks and hardware - and all this is made of metal.
At one point, manufacturers of aluminum structures found a solution to some pressing issues. One of the most thermally conductive materials (aluminum alloys) was decided to be divided by a less thermally conductive material. The multi-chamber profile was “cut” approximately in half and a polymer insert (“thermal bridge”) was made there. So that the bearing capacity would not be particularly affected, a new and rather expensive material was used - polyamide (often in combination with fiberglass).
The main idea of such constructive solutions is to increase the insulating properties, avoiding the creation of additional door blocks and vestibules.
Recently, high-quality entrance doors with thermal breaks assembled from imported profiles have appeared on the market. They are made using a similar technology as the "warm" aluminum systems. Only the bearing profile is created from rolled steel. Of course, there is no extrusion here - everything is done on bending equipment. The profile configuration is very complex; special grooves are made for the installation of a thermal bridge. Everything is arranged in such a way that the polyamide part with an H-shaped section becomes along the line of the canvas and connects both halves of the profile. The assembly of products is carried out by pressure (rolling), the connection of metal and polyamide can be glued.
From such profiles, the power frame of the canvas, racks and lintels of the frame, as well as the threshold are assembled. Naturally, there are some differences in the configuration of the section: the stiffener can be a simple square, and to provide a quarter or an influx of the web on the porch, it is a little more complicated. The sheathing of the power frame is made according to the traditional scheme, only with sheets of metal on both sides. The peephole is often abandoned.
By the way, there is an interesting system when the canvas on polymer harpoons (with elastic seals) is literally completely recruited from a profile with a thermal break. Its walls replace the sheathing sheets.
Naturally, “funny” doors appeared on the market, which mercilessly exploit the concept of a thermal break. At best, some tuning of an ordinary steel door is performed.
- First of all, manufacturers remove stiffeners. Immediately there are problems with the spatial rigidity of the canvas, resistance to deflection, "spike" opening of the skin, etc. As a way out, underdeveloped stiffeners are sometimes attached to the metal sheets of the skin. Some of them are fixed on the outer sheet, the other part - on the inner. In order to somehow stabilize the structure, the cavity is filled with foam, which simultaneously performs a shaping function and glues both sheets together. There are models where a metal mesh / grate is inserted into the foam so that an attacker cannot cut a through hole in the canvas.
- The extreme end faces of the leaf and the box can even have small separating inserts, however, with unknown characteristics. In general, the whole structure is not much different from ordinary Chinese doors. We just have a thin shell, only filled with foam.
Another trick is to take an ordinary door with ribs (given the cunning approach to business - usually low-grade) and insert cotton into the canvas and, in addition, a layer, for example, foam. After that, the product is awarded the title of "thermal break sandwich" and it is quickly sold as an innovative model. According to this principle, all steel door blocks can be recorded in this category, because insulation and decorative trim significantly reduce heat loss.
We also recommend
Smartphone xperia z5 premium black
Download toilet paper business plan
Description Nokia X2 dual sim on the Android platform, powerful processor and support for two sim cards
Is it possible to open a hostel in an apartment?
Services to the public: the most promising business ideas
How to start farming?
Loading...