Hvordan tredobbelte vinduer forhindrer energi (og penge) i at flyve ud ad vinduet

Det er tid til at skifte til tredobbelte vinduer. Sådan lyder budskabet fra en række undersøgelser ledet af Department of Energy's Pacific Northwest National Laboratory i samarbejde med en koalition af offentlige og private partnere.

"Lavere omkostninger, større tilgængelighed og drivkraften til at reducere CO2-emissioner skubber os mod et vendepunkt, hvor vinduer med tre vinduer begynder at give meget økonomisk mening," siger Kate Cort, forskningsøkonom ved PNNL og programleder for igangværende felt. valideringsundersøgelser af tredobbelte vinduer.

Det er ingen hemmelighed, at et hjems vinduer kan spilde meget energi. De kan lække luft, og selv de nyeste modeller af dobbeltrude vinduer bidrager væsentligt til energiforbruget og omkostningerne i et hjem. For et nyt hjem udgør vinduer typisk omkring 8 % af det udvendige areal, men er ansvarlige for halvdelen af ​​varmetabet eller -forstærkningen. Dette passive energitab gør vinduer til en væsentlig bidragyder til boligopvarmnings- og afkølingsomkostninger.

I mellemtiden er beviser for energi- og omkostningsbesparelser ved tre-rude vinduer langsomt blevet opbygget i årevis, siden de første prototyper blev introduceret omkring 1989. Tidligere undersøgelser har vist, at tre-rude vinduer er mere energieffektive end industristandard dobbelt-rude vinduer. rudeudvalg, men markedsadoptionen har været langsom på grund af omkostninger og tilgængelighed.

Disse ulemper er ved at ændre sig, sagde Cort. En ny generation af tynde tre-rude vinduer er billigere og kan lettere eftermonteres i eksisterende dobbelt-rude rammer. Som deres navn antyder, har tredobbelte vinduer tre glasruder, der skaber en dobbeltdækker sandwich, som bliver fyldt med en inert gas, såsom krypton, der giver yderligere isoleringskraft. Disse næste generations vinduer drager fordel af stordriftsfordele fra den samme avancerede glasfremstillingsteknologi, som fjerner tynde, men holdbare tv- og computerskærme.

I løbet af de seneste tre år har Cort og hendes kolleger systematisk evalueret de energibesparelser og økonomiske faktorer, der vil afgøre, hvor hurtigt de bliver accepteret af bygherrer. Dette arbejde blev støttet af DOE Building Technologies Office og Bonneville Power Administration.

Nu er statslige forsyningsmyndigheder begyndt at lægge mærke til det. For nylig brugte staten Michigan data fra en PNNL-feltundersøgelse af tredobbelte vinduer til at inkludere dem i statens tekniske ressourcemanual liste over godkendte energibesparende foranstaltninger, der er berettiget til forsyningsincitamenter og rabatter.

Nye energistandarder skaber et presserende behov

En anden nylig undersøgelse ledet af Cort, PNNL-kollegaen Edward Louie og Robert Hart fra Lawrence Berkeley National Laboratory viste, at tredobbelte vinduer til nybyggeri kan hjælpe bygherrer til en overkommelig pris med at opfylde strengere 2021-energikoder for nye hjem. Deres undersøgelse, offentliggjort i marts 2022-udgaven af ​​ASHRAE Journal viste, at når en boligbygger opgraderer vinduerne i et nyt hjem fra dobbelt- til tredobbelt rude, kan vinduernes energieffektivitet forbedres med 40 % eller mere. Denne ekstra ydeevne øger den samlede isoleringsværdi af hele hjemmets ydre, ofte omtalt som bygningens klimaskærm.

"Vores undersøgelse viste, at øget energieffektivitet af vinduer giver bygherrer mere fleksibilitet i design og mulighed for at foretage afvejninger med andre komponenter i konvolutten, såsom ydervægsisolering, mens de opfylder koden," sagde Cort. Den overordnede effekt er at give bygherrer flere muligheder og bedre sikkerhed for overholdelse af byggeregler, samtidig med at komforten for boligejere forbedres.

What's the hold up for triple-pane windows?

Builders play a key role in the adoption of new home building technologies, said Cort. In 2020, she and her colleagues interviewed 29 home builders who have participated in the DOE Zero Energy Ready Home program. They asked builders to explain their decision-making process for window selection during the 2018 to 2019 building season. Forty-one percent of these builders used triple‐pane windows in all their new homes and another 28% in most or some of their homes. For those who didn't use triple-pane windows, the biggest factor was cost.

"The price differential between double-pane and triple-pane windows has been a pain-point for builders," Cort noted. But she added that the increased incremental material cost of triple-pane windows is now about $700 to $2,400 for a 2,400-square-foot wood-framed home. This is about the same cost as adding an extra inch of rigid wall insulation to the same home.

Some builders also stated that the indirect cost of custom installation for triple-pane windows, which can be 25% to 50% heavier than similar sized double‐pane windows, also weighed into their choice.

"Most builders aren't familiar with the newer thinner, lighter triple-pane technology," said Cort. But the survey showed most would be willing to try them if the cost and availability made it practical for them.

Some of the builders Cort's team interviewed noted that consumers like the comfort and quiet of triple-pane windows. A recent study confirmed that the installation of thin triple-panes reduced the sound infiltration by an average of 8-10 decibels when compared to the home with double-pane metal-frame windows, which roughly equates to reducing the perceived noise level by half.

"When someone comes into the house and you shut the door, it's like getting into a Mercedes or BMW," said a Seattle builder. "It's so solid and quiet. We are building homes next to Boeing Field airport in Seattle. Planes are flying right overhead so close you can clearly see them from the houses, and it is so quiet inside you can't hear them."

Demonstration projects lead the way

When there are new approaches to home building, said Cort, builders need assurances that materials will be available when needed, hold up under use, and deliver on promised improvements.

To help meet those expectations, PNNL has joined forces with DOE, Lawrence Berkley National Laboratory, and the Northwest Energy Efficiency Alliance to launch the Partnership for Advanced Window Solutions. With support from DOE, this public-private partnership is working with builders, utilities, and manufacturers to both drive demand and scale up production of cost-effective "drop-in" thin triple-pane window designs and other high-performance window solutions.

The PNNL team recently compared the energy efficiency performance of these windows in its Lab Homes, a pair of identical manufactured homes used to study energy efficiency. During the winter heating season of 2019 and the summer cooling season of 2020, researchers recorded energy usage and temperatures throughout the homes. During the two 10-week evaluation periods, the windows saved an average of 12% on heating and 28% on cooling for the 1,500-square-foot structures. In addition, the home with the triple-pane windows reduced outdoor noise and maintained much more comfortable and even temperatures throughout the home during both summer and winter testing periods.

The research team is now field testing the windows in 10 locations nationwide, from manufactured homes in Pasco, Wash., to a net-zero apartment complex in Rotterdam, N.Y. In these field demonstration projects, the incremental cost over standard ENERGY STAR windows was $6 per square foot or less, said Cort. Within the last year, multiple versions of the thin-glass triple-pane units have been developed, certified by the National Fenestration Rating Council, and have become available to builders.

"At this point, it's a matter of increasing awareness among manufacturers, builders, utility programs, and consumers," said Cort. "It's time to look at windows, not just through them."