DK153417B

DK153417B - Underroof having a moisture-absorbent layer

Info

Publication number: DK153417B
Application number: DK418786A
Authority: DK
Inventors: Vagn Korsgaard
Original assignee: Vik Consult
Priority date: 1986-09-02
Filing date: 1986-09-02
Publication date: 1988-07-11
Also published as: DK418786A; DK153417C; DK418786D0

Description

Den foreliggende opfindelse angår et undertag til et tag med hældning og omfattende et fugtabsorberende lag.The present invention relates to a roof pitch for a pitched roof and comprising a moisture absorbing layer.

Almindeligvis monteres der under tagbelægninger med hældning, såsom teglstens-, skifer- og bølgeeternittage, et såkaldt undertag, hvis hovedformål er at forhindre, at slagregn eller fygesne, som trænger igennem de uundgåelige fuger i disse tagbelægninger, giver anledning til fugtskader.Generally, under roof roofs with slopes, such as brick, slate and corrugated roofing, are mounted, a so-called roof, the main purpose of which is to prevent the rains or pipes that penetrate the inevitable joints in these roof coatings cause moisture damage.

De kendte undertage består typisk af armerede plastfolier, som ikke alene er vandtætte men også diffusionstætte. Anvendelsen af sådanne undertage har medført det problem, at der i vinterhalvåret dannes kondensvand på undersiden af undertaget i så betydelige mængder, at det har givet anledning til fugtskader. For at forhindre dette stilles der i bygningsreglementet krav om, at tagrummet skal ventileres effektivt, hvilket i praksis ikke altid kan opfyldes.The known roof tops typically consist of reinforced plastic sheets, which are not only waterproof but also diffusion proof. The use of such roofs has led to the problem that in the winter season condensation water is formed on the underside of the roof in so large quantities that it has caused moisture damage. To prevent this, the building regulations require that the roof space be ventilated effectively, which in practice may not always be met.

Udnyttes tagrummet til beboelse, eller er der tale om, at loftet i underliggende rum følger tagfladen, såkaldte skrålofter, skal der desuden varmeisoleres imellem undertaget og selve loftsbeklædningen.If the roof space is used for habitation, or if the ceiling in the underlying room follows the roof surface, so-called sloping ceilings, thermal insulation must be provided between the ceiling and the ceiling covering itself.

For at forhindre, at der i disse tage dannes kondensvand på undertaget, kræves det, at der på isoleringens underside indlægges en dampspærre, samt at der imellem undertaget og isoleringen tilvejebringes et mindst 4 cm bredt hulrum, som skal ventileres til det fri. I praksis har det imidlertid vist sig vanskeligt at undgå dannelse af kondensvand, fordi dampspærren på isoleringens underside som regel ikke kan monteres tilstrækkeligt lufttæt til at forhindre, at fugtig luft fra det underliggende rum strømmer ud i tagkonstruktionen og afsætter kondensvand på undertaget.To prevent condensation from forming in the roof of these roofs, a vapor barrier must be installed on the underside of the insulation and a cavity at least 4 cm wide must be provided between the roof and the insulation. In practice, however, it has proved difficult to avoid condensation water formation because the vapor barrier on the underside of the insulation is usually not sufficiently airtight to prevent damp air from the underlying compartment from flowing into the roof structure and depositing condensation water on the ceiling.

Som følge af, at undertaget normalt er så nedbøjet mellem spærene, at det berører isoleringen på et større eller mindre areal mellem spærene, opnås der heller ikke den krævede ventilationsspalte mellem isoleringens overside og undertaget.Due to the fact that the ceiling is normally bent downwards between the rafters to affect the insulation on a larger or smaller area between the rafters, the required ventilation gap between the top and bottom of the insulation is also not obtained.

For at nedsætte risikoen for fugtskader på grund af dannelse af kondensvand på undertaget udføres dette nu ofte af materialer med en vis fugtakkumuleringsevne og en lille diffusionsmodstand med det formål at få det opsugede kondensvand til at diffundere ud igennem undertaget til hulrummet mellem tagbeklædningen og undertaget, der som regel er effektivt ventileret til det fri. Selv, når undertaget har en lille diffusionsmodstand, er det meget begrænset, hvor hurtigt det akkumulerede kondensvand kan slippe ud gennem undertaget. Dette skyldes, at de tynde folier, som typisk udgør undertaget, har en forsvindende lav varmemodstand i forhold til tagkonstruktionens samlede varmemodstand.To reduce the risk of moisture damage due to the formation of condensate water on the roof, this is often done by materials with a certain moisture accumulation ability and a small diffusion resistance in order to cause the sucked condensate to diffuse through the roof to the cavity between the roof covering and the roof. usually is effectively ventilated to the outside. Even when the subfloor has a small diffusion resistance, it is very limited how quickly the accumulated condensation water can escape through the subfloor. This is because the thin foils, which typically form the roof, have a vanishingly low heat resistance relative to the overall heat resistance of the roof structure.

I det vel ventilerede hulrum på oversiden af undertaget vil den relative luftfugtighed være den samme som i det fri, hvor den i vinterhalvåret typisk ligger meget nær 100%. Da temperaturen på den fugtige underside af undertaget vil være den samme som på oversiden, vil der følgelig ikke være nogen partialtrykforskel til at drive det akkumulerede kondensvand ud igennem undertaget. Kondensvandet vil derfor forblive i undertaget, indtil eventuel sol på taget vil drive det tilbage igennem isoleringen til dampspærren på undersiden af isoleringen, hvor det vil kondensere og ofte give anledning til dryp fra loftet, såkaldt sommerkondens.In the well-ventilated cavity on the upper surface of the roof, the relative humidity will be the same as in the open air, where it is typically very close to 100% during the winter season. Consequently, since the temperature of the humid underside of the sub-roof will be the same as on the upper side, there will be no partial pressure difference to drive the accumulated condensation water out through the sub-roof. The condensation water will therefore remain in the roof until any sun on the roof will drive it back through the insulation to the vapor barrier on the underside of the insulation, where it will condense and often give rise to dripping from the ceiling, so-called summer condensation.

i ·i ·

Undertaget ifølge opfindelsen er ejendommeligt ved, at oversiden af det fugtabsorberende lag er dækket af en vandtæt, diffusionsåben belægning, og at det på undersiden af det fugtabsorberende lag har adskilte zoner med en diffusionstæt belægning, idet disse zoner har en sådan størrelse og placering, at undertagets fugtafgivelse ved sollysbestråling af taget ikke er hurtigere, end at den afgivne fugt kan bortventileres fra undertagets underside.The subject matter of the invention is characterized in that the top surface of the moisture-absorbing layer is covered by a waterproof, diffusion-open coating and that on the underside of the moisture-absorbent layer has separate zones with a diffusion-tight coating, such zones having such size and location that the release of moisture from the roof by sunlight irradiation of the roof is not faster than that the released moisture can be vented from the underside of the roof.

Opfindelsen er baseret på den erkendelse, at sommerkondensdryp fra et undertag af den i indledningen nævnte art i det væsentlige helt kan elimineres ved at afstemme fugtafgivelsen fra det fugtabsorberende lag i retning bort fra tagfladen efter ventilationen langs undertagets underside, d.v.s. ventilationsspalten mellem undertaget og varmeisolationslaget, og at dette kan opnås ved at gøre dele af undersiden af det fugtabsorberende lag diffusionstæt.The invention is based on the recognition that summer condensate drip from a roof of the kind mentioned in the preamble can be substantially completely eliminated by tuning the moisture release from the moisture-absorbing layer away from the roof surface after ventilation along the underside of the roof, i.e.. the ventilation gap between the sub-roof and the heat insulation layer, and this can be achieved by rendering parts of the underside of the moisture-absorbing layer diffusion-proof.

De nævnte zoner dækker typisk et samlet areal på 70-90% og fortrinsvis ca. 80% af undersiden af det fugtabsorberende lag.The zones mentioned typically cover a total area of 70-90% and preferably about. 80% of the underside of the moisture-absorbing layer.

Af produktionsmæssige grunde har de nævnte zoner fortrinsvis form som striber, og undertaget oplægges fortrinsvis på en sådan måde, at striberne strækker sig fra tagets kip til dets fod. Undertiden er det dog mere hensigtsmæssigt at oplægge det på en sådan måde, at striberne forløber på tværs af taghældningen. Bredden af striberne bør ikke være større end halvdelen af vandets vandringslængde ved absorption i det absorberende lag, idet tagets absorptionsevne i modsat fald ikke vil blive fuldt udnyttet.For production reasons, said zones preferably take the form of stripes, and the roof is preferably positioned in such a way that the stripes extend from the roof of the roof to its foot. However, sometimes it is more appropriate to arrange it in such a way that the stripes extend across the roof slope. The width of the stripes should not be greater than half the length of the migration path of absorption in the absorbent layer, otherwise the absorbency of the roof will not be fully utilized.

Opfindelsen skal herefter beskrives nærmere under henvisning til tegningen, som viser et snit gennem et undertag ifølge opfindelsen i forstørret målestok.The invention will then be described in more detail with reference to the drawing, which shows an enlarged section through an upper roof according to the invention.

På tegningen betegner 1 et fugtabsorberende lag bestående af syntetiske formstoffibre. Laget er på oversiden belagt med en finperfo-reret, tynd plastfolie 2. På undersiden af det fugtabsorberende lag er der anbragt parallelle strimler 3 af en diffusionstæt plastfolie. Strimlerne 3 har en bredde, der er ca. 4 gange så stor som afstanden mellem strimlerne.In the drawing, 1 denotes a moisture-absorbing layer consisting of synthetic synthetic fibers. The top layer is coated with a fine-perforated, thin plastic film 2. On the underside of the moisture-absorbing layer, parallel strips 3 of a diffusion-tight plastic film are arranged. The strips 3 have a width of approx. 4 times the distance between the strips.

I praksis har det vist sig hensigtsmæssigt at belægge undersiden af det fugtabsorberende lag med striber med en bredde på ca. 20 cm, anbragt med et mellemrum på ca. 5 cm.In practice, it has been found convenient to coat the underside of the moisture-absorbing layer with strips having a width of approx. 20 cm, spaced approx. 5 cm.

Belægningen på oversiden af det fugtabsorberende lag består fortrinsvis af en finperforeret polyolefinfolie med en vægt på 15-25 2 2 g/m , f.eks. en polypropylenfolie med en vægt på ca. 20 g/m .The coating on the upper surface of the moisture-absorbing layer preferably consists of a finely perforated polyolefin film having a weight of 15-25 2 2 g / m, e.g. a polypropylene film having a weight of approx. 20 g / m.

Ved anvendelse af et fugtabsorberende lag bestående af fibre af polypropylenfilt kan perforeringen frembringes ved at presse den tynde polyolefinfolie mod en overflade med mange udragende fiberender. Disse udragende fiberender vil herved danne såkaldte pinholes, og der opnås hermed en tilfredsstillende damppermeabilitet.By using a moisture-absorbing layer consisting of polypropylene felt fibers, the perforation can be produced by pressing the thin polyolefin film onto a surface with many protruding fiber ends. These protruding fiber ends will thereby form so-called pinholes, thereby obtaining a satisfactory vapor permeability.

Folien på oversiden af undertaget kan bestå af en blanding af polyolefiner, f.eks. en hovedmængde polypropylen og en mindre mængde polyethylen. Folien indeholder fortrinsvis en antioxidant, såsom octadecyl-3-(3,5-ditertbutyl-4-hydroxy-phenyl)propionat, idet en oxidation af folien vil medføre, at den krakelerer. Herudover er det hensigtsmæssigt at tilføre folien et UV-beskyttelsesmiddel, såsom et metalpulver. Dette tjener navnlig til at beskytte folien i byggeperioden, hvor undertaget kan blive udsat for direkte sollys.The film on the upper side of the roof can consist of a mixture of polyolefins, e.g. a major amount of polypropylene and a smaller amount of polyethylene. The foil preferably contains an antioxidant such as octadecyl 3- (3,5-ditertbutyl-4-hydroxy-phenyl) propionate, as oxidation of the foil will cause it to crack. In addition, it is convenient to apply the film to a UV protective agent, such as a metal powder. In particular, this serves to protect the foil during the construction period, where the roof may be exposed to direct sunlight.

Det fugtabsorberende lag har fortrinsvis baneform og kan som nævnt bestå af polypropylenfilt. I så fald har laget fortrinsvis en vægt 2 på omkring 140 g/m . Det skal bemærkes, at laget også kan indeholde eller bestå af andre syntetiske fibre, herunder glasfibre, og at det helt eller delvis kan bestå af cel!ulosefibre. Laget har fortrinsvis en vægt på 100-200 g/m . De adskilte zoner på undertagets underside er fortrinsvis belagt med en diffusionstæt polyolefinfolie, f.eks.The moisture-absorbing layer preferably has a web shape and may, as mentioned, consist of polypropylene felt. In that case, the layer preferably has a weight 2 of about 140 g / m 2. It should be noted that the layer may also contain or consist of other synthetic fibers, including glass fibers, and may consist wholly or partially of cellulose fibers. The layer preferably has a weight of 100-200 g / m. Preferably, the separated zones on the underside of the undercoat are coated with a diffusion-tight polyolefin film, e.g.

2 en polypropylenfolie med en vægt på ca. 30 g/m .2 shows a polypropylene film having a weight of approx. 30 g / m.

Striberne på undertagets underside fremstilles fortrinsvis ved samtidigt at føre det fugtabsorberende lag under et antal dyser, hvorfra der afgives strømme af flydende plast med en bredde, som er lidt større end bredden af de ønskede foliestrimler, og ved derpå at føre det således dannede materiale gennem et valsesæt.The strips on the underside of the undercoat are preferably made by simultaneously passing the moisture-absorbing layer under a number of nozzles from which flows of liquid plastic having a width slightly greater than the width of the desired foil strips, and then passing the material thus formed through a roller set.

Claims

1. A roof tile roof comprising a moisture-absorbing layer, characterized in that the top surface of the moisture-absorbing layer is covered by a waterproof, diffusion-open coating and has separate zones with a diffusion-proof coating on the underside of the moisture-absorbing layer. these zones are of such size and location that the moisture release of the ceiling by sunlight irradiation of the roof is not faster than the moisture released can be vented from the underside of the roof.

Cover according to claim 1, characterized in that the coating on the upper side of the moisture-absorbing layer consists of a finely perforated plastic film.

The roof according to claim 1, characterized in that the separate zones on the underside are in the form of stripes and that the diffusion-proof coating consists of plastic foil strips.

The roof according to claim 3, characterized in that the distance between the coated stripes is approx. 1/4 of the width of their width.