Wholesale Energy Efficient UPVC Doors for Entrance Retrofit and New Build

An energy efficient UPVC door rated at 1.00 W/m2K reads 1.68 once it is in a wall, because the 1 m threshold under it can add as much heat loss as 38 per cent of the whole leaf. The leaf is rarely the weak line; the line it stands on is.

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What U value does the leaf of an energy efficient UPVC door actually reach?

Between 0.95 and 1.10 W/m2K with a 28 mm triple unit, argon fill and two low-e surfaces, on a five chamber PVC-U profile with galvanised steel reinforcement in the sash and the frame. With a 24 mm double unit the same leaf sits at 1.25 to 1.40. Both figures are for the leaf alone, measured over the leaf area on a test report, and both are arithmetic once the glass and the frame values are known.

The leaf is 2.1 m2 of a door that occupies 2.1 m2 of wall, so it carries almost all of the area. That is why a supplier can quote 1.00 and be honest about it, and why the installed number still comes out 68 per cent higher. The gap between the two figures is the perimeter, and the perimeter is where the money is either spent or lost.

The profile choice behind that leaf is worth fixing early, since a five chamber section with a steel liner is what keeps the sash straight on a 2.1 m leaf; the chamber count and the reinforcement are compared on UPVC door profiles.

Why does the same energy efficient UPVC door read 1.24 or 1.68 once it is fitted?

Because the installed value is an area weighted average of the leaf plus the linear junctions around it. The arithmetic is simple enough to do on a quote: U installed equals leaf U times leaf area, plus each junction coefficient times its length, all divided by the same leaf area. With 2.1 m2 of leaf at 1.00, 4.2 m of jamb and head at 0.05, and 1.0 m of thermally broken threshold at 0.30, the result is 1.24.

Change only the threshold, to a plain aluminium sill sitting straight on the screed at 0.80, and lift the jambs to a 0.15 detail with no frame insulation, and the same leaf returns 1.68. Nothing about the door changed. The glass, the profile, the gasket and the hinges are identical, and the buyer has paid for a 1.00 door and received a 1.68 opening.

Leaf 1.00 W/m2K over 2.1 m2 in every row. U installed = (1.00 x 2.1 + psi jamb x 4.2 + psi sill x 1.0) / 2.1. Psi values are the usual range for these details in EN ISO 10077-2 tabulations and are confirmed by a project specific calculation. Calculated, not measured.

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Why is the threshold worse than the jambs?

Three reasons stack up. The jamb has a wall behind it, so the insulation of the wall can be returned into the reveal and the junction stays warm. The threshold has a floor behind it, and a floor is a slab edge or a screed over a slab, which is a much better conductor and is usually already built when the door arrives. And a door threshold has to be walkable, so it cannot be 100 mm of insulation; it is a 3 to 5 mm aluminium or steel section with a gasket line above it.

The numbers follow that geometry. A 0.80 W/(m K) sill is not an unusual figure for an aluminium threshold bedded on mortar with no separator; a thermally broken sill with a PVC or polyamide separator sits near 0.30, and a sill set on a 20 mm insulation pad with the leaf lapping it lands near 0.10. The same 1 m of line, three different buildings.

The leaf also has a gap at the bottom that no other edge has, 5 to 8 mm of clearance so it can swing, closed by a drop seal or a brush. A drop seal stops air; it does not stop heat, and the cold bridge runs under it through the sill. That is why a door can pass an air permeability test to EN 12207 and still show a wet line on the floor in January, and why the threshold detail belongs in the order and in the site instructions of any energy efficient UPVC door.

At what outdoor temperature does the threshold start to run with water?

The temperature factor f is what decides it: f equals the difference between the inner surface and the outdoor air, divided by the difference between indoor and outdoor air. EN ISO 13788 asks for 0.70 on residential junctions. With 20 C inside and 50 per cent relative humidity, the dew point is 9.3 C, and solving f = (9.3 - outdoor) / (20 - outdoor) gives the outdoor temperature at which the surface reaches dew point.

A plain sill at f 0.60 reaches dew point at about minus 7 C. A thermally broken sill at f 0.78 holds until about minus 29 C. The 0.70 line sits at minus 16 C, which is the number to quote when a buyer asks whether the door is fit for a cold climate: the leaf passes, and the sill is the part that decides the answer.

The visible symptom arrives before the calculation does. Water sits on the floor line inside the door, the paint on the reveal lifts within two winters, and the bottom rail of the leaf shows a dark line where the gasket has been wet for months. On a refurbishment the cheapest moment to fix all three is before the new door is ordered, while the sill can still be changed, and the same logic runs through humid coastal climates.

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What can the order fix before an energy efficient UPVC door is fabricated?

Four things, all of them cheap at order stage and expensive afterwards. The threshold type, written as a psi value and not as a material name. The sill upstand and the drainage path, so water leaves the frame outward. The jamb detail with its insulation return, which is a wall item that the door supplier has to draw anyway. And the clearance under the leaf with the seal that closes it, because 8 mm of open gap undoes a 1.00 leaf in one winter.

Send the wall build up and the floor detail to kristin@haolvbuilding.com and the installed U value comes back with the threshold marked, so the choice between 1.24 and 1.68 is made on paper. It takes one drawing and one calculation, and it is the only point in the project where the sill can still be changed at no cost.

One sentence to put in every enquiry: the U value required is a whole opening value, quoted with the junction details. A supplier who answers with a leaf figure has answered a different question, and the difference is the 0.44 W/m2K that decides whether the entrance meets the target. Openings where the leaf is the fixed part and the frame carries the seals are compared on UPVC French doors.

Which build suits which entrance?

Read the table by entrance type. A sheltered porch tolerates a plain sill because it never sees driving rain or a long cold soak. An exposed entrance does not, and the difference in price between the two sills is small against the cost of taking a door out again. The glass line is the one that changes the leaf U value, and the threshold line is the one that changes what the buyer actually gets. Leaf layouts and panel finishes across the range are collected under UPVC door styles.

Usual range for this family. Leaf U values are the ones stated on test reports for the leaf alone; installed values are area weighted from the junction details in the row, calculated, not measured. Psi values are confirmed by a project specific EN ISO 10077-2 calculation.

Frequently asked questions

What is the minimum order for an energy efficient UPVC door and how long is production? Minimum order is 10-20 units and lead time is 25-30 days from drawing approval. Mixed leaf widths in one batch are normal, and each threshold type is confirmed on the schedule before cutting.

What does a thermally broken threshold add to the price? It is a small line against the door: the sill changes from a plain section to one with a separator and a drainage chamber, and the cost moves in single figures per unit. Against that, the same door drops from 1.68 to 1.24 installed, which is the cheapest 0.44 W/m2K in the whole entrance.

Can an energy efficient UPVC door be supplied with a low threshold for level access? Yes, and the threshold gets harder to keep warm as it gets lower, because there is less depth for a separator and less height for a drainage chamber. On a level access detail ask for the psi value of the sill being offered, together with the drainage route, and check both against the floor finish.

Does the door need a drain in front of the threshold? It needs a drainage path, which is usually a slope or a channel outside the frame line. A door with a drainage chamber inside the sill and nowhere for the water to go will discharge it onto the floor it was meant to protect, and that failure looks exactly like a leaking gasket.

Ordering from Haolv

Haolv Building Materials Co., Ltd. has been making doors and windows for 19 years, energy efficient UPVC doors among them, and returns an installed U value against the wall and floor details supplied with the enquiry. Certification for the profiles and the glazing is available on request with the quotation. Minimum order is 10-20 units and lead time is 25-30 days.

Send the wall build up to kristin@haolvbuilding.com, or start from Haolv Building Materials Co., Ltd. and the threshold detail, the psi values and the installed U value come back with the quotation.

What this guide claims and what it does not: the leaf values are the ones stated on test reports for the leaf alone, the installed values are area weighted arithmetic on the psi values in each row, and the psi values themselves are the usual range for those details, confirmed by a project specific calculation. The condensation temperatures follow from the temperature factor, not from a monitored door. Nothing here comes from a measured installation.

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References

1. EN 14351-1:2006+A2:2016 — Windows and doors. Product standard, characteristics and performance.
2. EN ISO 10077-1:2017 — Thermal performance of windows, doors and shutters. Calculation of thermal transmittance. General.
3. EN ISO 10077-2:2017 — Thermal performance of windows, doors and shutters. Numerical method for frames.
4. EN ISO 13788:2012 — Hygrothermal performance of building components. Internal surface temperature to avoid critical surface humidity and interstitial condensation.
5. EN 12207:2017 — Windows and doors. Air permeability, classification.
6. EN 12208:2000 — Windows and doors. Watertightness, classification.

The installed U values in this guide are area weighted from the leaf value and the psi values stated in each table. They are arithmetic, not measurements from a fitted door, and the psi value of every junction is confirmed by a project specific EN ISO 10077-2 calculation before the order is released.