Owens Corning (OC) POSASR Automatic shelf registration (post-effective amendment)

Exhibit 5.1

NORTH POINT • 901 LAKESIDE AVENUE • CLEVELAND, OHIO 44114.1190

TELEPHONE: +1.216.586.3939 • FACSIMILE: +1.216.579.0212

May 31, 2018

Owens Corning

One Owens Corning Parkway

Toledo, Ohio 43659

Re: Registration Statement on Form S-3 Filed by Owens Corning

Ladies and Gentlemen:

We have acted as counsel for Owens Corning, a Delaware corporation (the “Company”), in connection with the authorization of the issuance and sale from time to time, on a delayed basis, by the Company, of an indeterminate amount of: (i) shares of common stock, par value $0.01 per share, of the Company (the “Common Stock”); and (ii) debt securities of the Company (the “Debt Securities”), in one or more series, certain of which may be convertible into or exchangeable for other securities of the Company, in each case, as contemplated by the Registration Statement on Form S-3 (Registration No. 333-222514), as amended by a Post-Effective Amendment No. 1 to which this opinion is filed as an exhibit (as the same may be amended from time to time, the “Registration Statement”). The Common Stock and the Debt Securities are collectively referred to herein as the “Securities.” The Securities may be offered and sold from time to time pursuant to Rule 415 under the Securities Act of 1933 (the “Securities Act”).

In connection with the opinions expressed herein, we have examined such documents, records and matters of law as we have deemed relevant or necessary for purposes of such opinions. Based on the foregoing, and subject to the further assumptions, qualifications and limitations set forth herein, we are of the opinion that:

1. The shares of Common Stock, upon receipt by the Company of such lawful consideration therefor as the Company’s Board of Directors (or an authorized committee thereof) may determine, will be validly issued, fully paid and nonassessable.

2. The Debt Securities, upon receipt by the Company of such lawful consideration therefor as the Company’s Board of Directors (or an authorized committee thereof) may determine, will constitute valid and binding obligations of the Company.

ALKHOBAR • AMSTERDAM • ATLANTA • BEIJING • BOSTON • BRISBANE • BRUSSELS • CHICAGO • CLEVELAND • COLUMBUS • DALLAS

DETROIT • DUBAI • DÜSSELDORF • FRANKFURT • HONG KONG • HOUSTON • IRVINE • LONDON • LOS ANGELES • MADRID • MELBOURNE

MEXICO CITY • MIAMI • MILAN • MINNEAPOLIS • MOSCOW • MUNICH • NEW YORK • PARIS • PERTH • PITTSBURGH • RIYADH

SAN DIEGO • SAN FRANCISCO • SÃO PAULO • SHANGHAI • SILICON VALLEY • SINGAPORE • SYDNEY • TAIPEI • TOKYO • WASHINGTON

In rendering the foregoing opinions, we have assumed that: (i) the Registration Statement, and any amendments thereto, will have become effective (and will remain effective at the time of issuance of any Securities thereunder); (ii) a prospectus supplement describing each class and/or series of Securities offered pursuant to the Registration Statement, to the extent required by applicable law and relevant rules and regulations of the Securities and Exchange Commission (the “Commission”), will be timely filed with the Commission; (iii) the definitive terms of each class and/or series of Securities will have been established in accordance with the authorizing resolutions adopted by the Company’s Board of Directors (or an authorized committee thereof), the organizational documents of the Company and applicable law; (iv) the Company will issue and deliver the Securities in the manner contemplated by the Registration Statement and any Securities that consist of shares of Common Stock will have been authorized and reserved for issuance, in each case within the limits of the then remaining authorized but unissued and unreserved amounts of such Common Stock; (v) the resolutions authorizing the Company to issue, offer and sell the Securities will have been adopted by the Company’s Board of Directors (or an authorized committee thereof) and will be in full force and effect at all times at which the Securities are offered or sold by the Company; (vi) all Securities will be issued in compliance with applicable federal and state securities laws; and (vii) the Indenture (as defined below) will be governed by and construed in accordance with the laws of the State of New York and will constitute a valid and binding obligation of each party thereto other than the Company.

For purposes of the opinions expressed herein, we have further assumed that: (i) the Debt Securities will have been issued pursuant to an Indenture, dated as of June 2, 2009, by and among the Company, the guarantors party thereto and Wells Fargo Bank, National Association, as trustee (the “Trustee”), as amended and supplemented from time to time (the “Indenture”); (ii) all terms of the Debt Securities not provided for in the Indenture will have been established in accordance with the provisions of the Indenture and reflected in appropriate documentation approved by us and, if applicable, executed and delivered by the Company and the Trustee; and (iii) the Debt Securities will be executed, authenticated, issued and delivered in accordance with the provisions of the Indenture.

The opinion expressed in paragraph 2 is limited by bankruptcy, insolvency, reorganization, fraudulent transfer and fraudulent conveyance, voidable preference, moratorium or other similar laws and related regulations and judicial doctrines from time to time in effect relating to or affecting creditors’ rights generally, and by general equitable principles and public policy considerations, whether such principles and considerations are considered in a proceeding at law or equity.

As to facts material to the opinions and assumptions expressed herein, we have relied upon oral or written statements and representations of officers and other representatives of the Company and others.

The opinions expressed herein are limited to the General Corporation Law of the State of Delaware and the laws of the State of New York, in each case as currently in effect, and we express no opinion as to the effect of the laws of any other jurisdiction.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to Jones Day under the caption “Legal Matters” in the prospectus constituting a part of such Registration Statement. In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Jones Day